博客> NSString、NSMutableString、NSMutableArray、NSMutableDictionary等防崩溃策略(运行时替换原生方法)
NSString、NSMutableString、NSMutableArray、NSMutableDictionary等防崩溃策略(运行时替换原生方法)
2017-09-22 15:47 评论:0 阅读:384 方金峰
ios NSString runtime 运行时 NSMutableString NSMutableArray NSMutableDictionary 防崩溃

由于上一篇文章中,很多人都说通过类别拓展,添加新方法,然后对新方法进行判断,来达到防止崩溃的目的,这样做法不利于项目的维护和后期的扩展,毕竟长期以来大家习惯了用系统自带的方法。所以最好的方法就是在系统方法里面判断,因此研究了下,通过runtime机制替换了系统的方法,来对参数添加判断,以此来防止崩溃现象。主要启发自这篇文章:

从NSArray看类簇,这篇文章比较详细介绍了类簇的设计模式。

一.原理

1.由于NSString、NSArray、NSMutableString、NSMutableArray、NSMutableDictionary这几个类型都是Class Clusters(类簇)设计模式设计出来的,它们偷偷隐藏了很多具体的实现类, 只暴露出简单的接口来供外层调用,实现了很好的封装。

首先我们利用 NSArray 的几个方法来创建实例对象:

(lldb) po [NSArray array]
<__NSArray0 0x600000017670>(
)
(lldb) po [NSArray arrayWithObject:@"Hello,Zie"];
<__NSSingleObjectArrayI 0x600000017680>(
Hello,Zie
)
po [NSArray arrayWithObjects:@1,@2, nil];
<__NSArrayI 0x100500050>(
1,
2
)

通过打印可以看到由 NSArray ,创建的对象并不是 NSArray 本身,有可能是 <NSArray0 、 NSSingleObjectArrayI 、 __NSArrayI >, 这里 NSArray 就是那个抽象类,而被创建出来那些奇奇怪的类就是作为具体的实现类,同时是内部私有的。 所以通过运行时的class_addMethod和class_replaceMethod来添加方法或是通过method_exchangeImplementations来替换系统中对应的原生方法必须依据它具体的实现类,也就是说必须依据<NSArray0 、 NSSingleObjectArrayI 、 __NSArrayI>这三者,而不能依据NSArray。

二.具体实现:以NSString和NSMutableArray为例

1.NSString:

NSString实例类型.png

经发现NSString实际的实现类有<NSCFConstantString、NSTaggedPointerString、NSCFString>这三者,由于NSMutableString主要实现类是<__NSCFString>,所以将<__NSCFString>相应的替代方法放到NSMutableString相关文件里面。

#import <objc>
#import "NSString+Safe.h"

@implementation NSString (Safe)

#pragma mark --- init method

+ (void)load {
    //只执行一次这个方法
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        NSString *tmpSubFromStr = @"substringFromIndex:";
        NSString *tmpSafeSubFromStr = @"safe_substringFromIndex:";
        NSString *tmpSafePointSubFromStr = @"safePoint_substringFromIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafeSubFromStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafePointSubFromStr];

       NSString *tmpSubToStr = @"substringToIndex:";
        NSString *tmpSafeSubToStr = @"safe_substringToIndex:";
        NSString *tmpSafePointSubToStr = @"safePoint_substringToIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubToStr newMethodStr:tmpSafeSubToStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubToStr newMethodStr:tmpSafePointSubToStr];

        NSString *tmpSubRangeStr = @"substringWithRange:";
        NSString *tmpSafeSubRangeStr = @"safe_substringWithRange:";
        NSString *tmpSafePointSubRangeStr = @"safePoint_substringWithRange:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubRangeStr newMethodStr:tmpSafeSubRangeStr];

       [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubRangeStr newMethodStr:tmpSafePointSubRangeStr];

        NSString *tmpRangeOfStr = @"rangeOfString:options:range:locale:";
        NSString *tmpSafeRangeOfStr = @"safe_rangeOfString:options:range:locale:";
        NSString *tmpSafePointRangeOfStr = @"safePoint_rangeOfString:options:range:locale:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpRangeOfStr newMethodStr:tmpSafeRangeOfStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpRangeOfStr newMethodStr:tmpSafePointRangeOfStr];

    });

}


这里因为将<__NSCFString>放到NSMutableString类别里面去替换,所以只做实例类<__NSCFConstantString、NSTaggedPointerString>的替换。 因为最终调用替换函数:method_exchangeImplementations(originalMethod, swizzledMethod);,所以

NSString *tmpSubFromStr = @"substringFromIndex:"; 
NSString *tmpSafeSubFromStr = @"safe_substringFromIndex:"; 
NSString *tmpSafePointSubFromStr = @"safePoint_substringFromIndex:";

每一个实例类别都应该有自己相对应的替换方法,这里tmpSubFromStr是系统的方法,tmpSafeSubFromStr是<__NSCFConstantString>实例类对应的替换方法,tmpSafePointSubFromStr是NSTaggedPointerString对应的替换方法。这里虽然是NSString,可以通过

SEL originalSelector = NSSelectorFromString(originalMethodStr); 
SEL swizzledSelector = NSSelectorFromString(newMethodStr);

转换成相应的SEL方法。如果每个实力类没有自己对应的方法,比如说像这样:

NSString *tmpSubFromStr = @"substringFromIndex:";
NSString *tmpSafeSubFromStr = @"safe_substringFromIndex:";

[self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafeSubFromStr];

[self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafeSubFromStr];

那最终只会对NSTaggedPointerString原来的substringFromIndex:函数进行替换,<__NSCFConstantString>实例类型的就不起作用。

// 获取 method
+ (Method)methodOfClassStr:(NSString *)classStr selector:(SEL)selector {
    return class_getInstanceMethod(NSClassFromString(classStr),selector);
}

// 判断添加 新方法 或 新方法 替换 原来 方法
+ (void)exchangeImplementationWithClassStr:(NSString *)classStr originalMethodStr:(NSString *)originalMethodStr newMethodStr:(NSString *)newMethodStr {

    SEL originalSelector = NSSelectorFromString(originalMethodStr);
    SEL swizzledSelector = NSSelectorFromString(newMethodStr);

    Method originalMethod = [NSString methodOfClassStr:classStr selector:NSSelectorFromString(originalMethodStr)];
    Method swizzledMethod = [NSString methodOfClassStr:classStr selector:NSSelectorFromString(newMethodStr)];

    // 判断 是否 可以添加 新方法
    BOOL didAddMethod =
class_addMethod(NSClassFromString(classStr),
                originalSelector,
                method_getImplementation(swizzledMethod),
                method_getTypeEncoding(swizzledMethod));

    if (didAddMethod) {
        class_replaceMethod(NSClassFromString(classStr),
                        swizzledSelector,
                        method_getImplementation(originalMethod),
                        method_getTypeEncoding(originalMethod));

    } else {
        // 替换 原有 方法
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
}


这段代码主要通过运行时,先判断是否可以往该实际类里面添加新方法,如果可以则添加新方法,如果不行,则替换原有的方法。但我们要替换的函数一般系统包含,所以只会走替换函数method_exchangeImplementations,但为了系统的健壮性,还是有必要先进行判断。

#pragma mark --- implement method
/****************************************  substringFromIndex:  ***********************************/
/**
 从from位置截取字符串 对应 __NSCFConstantString

 @param from 截取起始位置
 @return 截取的子字符串
 */
- (NSString *)safe_substringFromIndex:(NSUInteger)from {
    if (from > self.length ) {
        return nil;
    }
    return [self safe_substringFromIndex:from];
}
/**
 从from位置截取字符串 对应  NSTaggedPointerString

 @param from 截取起始位置
 @return 截取的子字符串
 */
- (NSString *)safePoint_substringFromIndex:(NSUInteger)from {
    if (from > self.length ) {
        return nil;
    }
    return [self safePoint_substringFromIndex:from];
}

/****************************************  substringFromIndex:  ***********************************/
/**
 从开始截取到to位置的字符串  对应  __NSCFConstantString

 @param to 截取终点位置
 @return 返回截取的字符串
 */
- (NSString *)safe_substringToIndex:(NSUInteger)to {
    if (to > self.length ) {
        return nil;
    }
    return [self safe_substringToIndex:to];
}

/**
 从开始截取到to位置的字符串  对应  NSTaggedPointerString

 @param to 截取终点位置
 @return 返回截取的字符串
 */
- (NSString *)safePoint_substringToIndex:(NSUInteger)to {
   if (to > self.length ) {
        return nil;
    }
    return [self safePoint_substringToIndex:to];
}

/*********************************** rangeOfString:options:range:locale:  ***************************/
/**
 搜索指定 字符串  对应  __NSCFConstantString

 @param searchString 指定 字符串
 @param mask 比较模式
 @param rangeOfReceiverToSearch 搜索 范围
 @param locale 本地化
 @return 返回搜索到的字符串 范围
 */
- (NSRange)safe_rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale {
    if (!searchString) {
        searchString = self;
    }

    if (rangeOfReceiverToSearch.location > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if (rangeOfReceiverToSearch.length > self.length) {
         rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if ((rangeOfReceiverToSearch.location + rangeOfReceiverToSearch.length) > self.length) {
         rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    return [self safe_rangeOfString:searchString options:mask range:rangeOfReceiverToSearch locale:locale];
}

/**
 搜索指定 字符串  对应  NSTaggedPointerString

 @param searchString 指定 字符串
 @param mask 比较模式
 @param rangeOfReceiverToSearch 搜索 范围
 @param locale 本地化
 @return 返回搜索到的字符串 范围
 */
- (NSRange)safePoint_rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale {
    if (!searchString) {
        searchString = self;
    }

    if (rangeOfReceiverToSearch.location > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if (rangeOfReceiverToSearch.length > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if ((rangeOfReceiverToSearch.location + rangeOfReceiverToSearch.length) > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    return [self safePoint_rangeOfString:searchString options:mask range:rangeOfReceiverToSearch locale:locale];
}

/*********************************** substringWithRange:  ***************************/
/**
 截取指定范围的字符串  对应  __NSCFConstantString

 @param range 指定的范围
 @return 返回截取的字符串
 */
- (NSString *)safe_substringWithRange:(NSRange)range {
    if (range.location > self.length) {
        return nil;
    }

    if (range.length > self.length) {
        return nil;
    }

    if ((range.location + range.length) > self.length) {
        return nil;
    }
    return [self safe_substringWithRange:range];
}

/**
 截取指定范围的字符串 对应  NSTaggedPointerString

 @param range 指定的范围
 @return 返回截取的字符串
 */
- (NSString *)safePoint_substringWithRange:(NSRange)range {
    if (range.location > self.length) {
        return nil;
    }

    if (range.length > self.length) {
        return nil;
    }

    if ((range.location + range.length) > self.length) {
        return nil;
    }
    return [self safePoint_substringWithRange:range];
}
@end

这里是具体的替换方法,对传入的参数进行判断,如果参数合理,就执行原来系统的方法,如果参数不合理,就直接返回适当内容(一般返回nil或直接return);这里主要说一点:

// __NSCFConstantString 类型
NSString *tmpConstantString = @"432423432432432432";
[tmpConstantString rangeOfString:nil];

比如说系统原有的rangeOfString:函数,当你传入为nil的时候,就会导致崩溃,所以你很容易,就会去替换掉系统的该函数,但这是没有效果的, NSString的rangeOfString.png 从这里我们可以看出来,真正导致系统崩溃的是rangeOfString:options:range:locale:执行了系统的该函数,所以应该去替换的是系统的rangeOfString:options:range:locale:这个函数。

同样的NSMutableArray:

// __NSArrayM 类型
NSMutableArray *tmpMutableArrayM = [NSMutableArray arrayWithCapacity:0];
[tmpMutableArrayM removeObjectAtIndex:1000];

NSMutableArray的removeObjectAtIndex函数传入一个超过数组本身长度的索引,就会导致崩溃,所以你去替换系统的removeObjectAtIndex方法这样也是没有效果的 NSMutableArray的removeObjectAtIndex.png

因为真正导致该崩溃的因为是因为系统执行了removeObjectsInRange:函数,函数里面的参数range超出了数组的范围,需要对该参数进行判断,才能有效的防止崩溃,所以替换系统的方法,必须先清楚引起系统崩溃的具体原因,才能对症下药。

2.NSMutableArray:

NSMutableArray主要原理跟NSString是一样的,但这里有一点需要注意的:

由于NSArray和NSMutableArray里面都有objectAtIndex这个原生函数,但是NSArray和NSMutableArray的实际类不一样,所以NSArray和NSMutableArray里面的替换方法必须不一样,否则因为替换 method_exchangeImplementations(originalMethod, swizzledMethod);只是简单的进行将新方法替换掉原有的方法,但是它并没有类别的区分,所以如果NSArray和NSMutableArray里面的替换方法一样,那就只会执行NSMutableArray里面的替换方法,NSArray里面的不起作用(NSArray里面的load方法先执行)。

三.总结:

1.NSArray

主要替换objectAtIndex:方法

+ (void)load {
    //只执行一次这个方法
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        //替换 objectAtIndex
        NSString *tmpStr = @"objectAtIndex:";
        NSString *tmpFirstStr = @"safe_ZeroObjectAtIndex:";
        NSString *tmpThreeStr = @"safe_objectAtIndex:";
        NSString *tmpSecondStr = @"safe_singleObjectAtIndex:";

        [self exchangeImplementationWithClassStr:@"__NSArray0" originalMethodStr:tmpStr newMethodStr:tmpFirstStr];

        [self exchangeImplementationWithClassStr:@"__NSSingleObjectArrayI" originalMethodStr:tmpStr newMethodStr:tmpSecondStr];

        [self exchangeImplementationWithClassStr:@"__NSArrayI" originalMethodStr:tmpStr newMethodStr:tmpThreeStr];
    });
}

实现方法:

#pragma mark --- implement method

/**
 取出NSArray 第index个 值 对应 __NSArrayI

 @param index 索引 index
 @return 返回值
 */
- (id)safe_objectAtIndex:(NSUInteger)index {
    if (index >= self.count){
        return nil;
    }
    return [self safe_objectAtIndex:index];
}

/**
 取出NSArray 第index个 值 对应   __NSSingleObjectArrayI

 @param index 索引 index
 @return 返回值
 */
- (id)safe_singleObjectAtIndex:(NSUInteger)index {
    if (index >= self.count){
        return nil;
    }
    return [self safe_singleObjectAtIndex:index];
}

/**
 取出NSArray 第index个 值 对应 __NSArray0

 @param index 索引 index
 @return 返回值
 */
- (id)safe_ZeroObjectAtIndex:(NSUInteger)index {
    if (index >= self.count){
        return nil;
    }
    return [self safe_ZeroObjectAtIndex:index];
}

2.NSMutableArray

主要替换方法:objectAtIndex:、removeObjectsInRange:、insertObject:atIndex:、removeObject:inRange:这几个方法

+ (void)load {
    //只执行一次这个方法
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        //替换 objectAtIndex:
        NSString *tmpGetStr = @"objectAtIndex:";
        NSString *tmpSafeGetStr = @"safeMutable_objectAtIndex:";
        [self exchangeImplementationWithClassStr:@"__NSArrayM" originalMethodStr:tmpGetStr newMethodStr:tmpSafeGetStr];

        //替换 removeObjectsInRange:
        NSString *tmpRemoveStr = @"removeObjectsInRange:";
        NSString *tmpSafeRemoveStr = @"safeMutable_removeObjectsInRange:";

        [self exchangeImplementationWithClassStr:@"__NSArrayM" originalMethodStr:tmpRemoveStr newMethodStr:tmpSafeRemoveStr];

        //替换 insertObject:atIndex:
        NSString *tmpInsertStr = @"insertObject:atIndex:";
        NSString *tmpSafeInsertStr = @"safeMutable_insertObject:atIndex:";

        [self exchangeImplementationWithClassStr:@"__NSArrayM" originalMethodStr:tmpInsertStr newMethodStr:tmpSafeInsertStr];

        //替换 removeObject:inRange:
        NSString *tmpRemoveRangeStr = @"removeObject:inRange:";
        NSString *tmpSafeRemoveRangeStr = @"safeMutable_removeObject:inRange:";

        [self exchangeImplementationWithClassStr:@"__NSArrayM" originalMethodStr:tmpRemoveRangeStr newMethodStr:tmpSafeRemoveRangeStr];

    });
}

实现方法:

pragma mark --- implement method

/**
 取出NSArray 第index个 值

 @param index 索引 index
 @return 返回值
 */
- (id)safeMutable_objectAtIndex:(NSUInteger)index {
    if (index >= self.count){
        return nil;
    }
    return [self safeMutable_objectAtIndex:index];
}

/**
 NSMutableArray 移除 索引 index 对应的 值

 @param range 移除 范围
 */
- (void)safeMutable_removeObjectsInRange:(NSRange)range {

    if (range.location > self.count) {
        return;
    }

    if (range.length > self.count) {
        return;
    }

    if ((range.location + range.length) > self.count) {
        return;
    }

     return [self safeMutable_removeObjectsInRange:range];
}

/**
 在range范围内, 移除掉anObject

 @param anObject 移除的anObject
 @param range 范围
 */
- (void)safeMutable_removeObject:(id)anObject inRange:(NSRange)range {
    if (range.location > self.count) {
        return;
    }

    if (range.length > self.count) {
        return;
    }

    if ((range.location + range.length) > self.count) {
        return;
    }

    if (!anObject){
        return;
    }

    return [self safeMutable_removeObject:anObject inRange:range];

}

/**
 NSMutableArray 插入 新值 到 索引index 指定位置

 @param anObject 新值
 @param index 索引 index
 */
- (void)safeMutable_insertObject:(id)anObject atIndex:(NSUInteger)index {
    if (index > self.count) {
            return;
    }

    if (!anObject){
        return;
    }

    [self safeMutable_insertObject:anObject atIndex:index];
}

3.NSString

主要替换方法:substringFromIndex:,substringToIndex:,substringWithRange:,rangeOfString:options:range:locale:这几个主要方法

+ (void)load {
    //只执行一次这个方法
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        // 替换 substringFromIndex:
        NSString *tmpSubFromStr = @"substringFromIndex:";
        NSString *tmpSafeSubFromStr = @"safe_substringFromIndex:";
        NSString *tmpSafePointSubFromStr = @"safePoint_substringFromIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafeSubFromStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafePointSubFromStr];

        // 替换 substringToIndex:
        NSString *tmpSubToStr = @"substringToIndex:";
        NSString *tmpSafeSubToStr = @"safe_substringToIndex:";
        NSString *tmpSafePointSubToStr = @"safePoint_substringToIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubToStr newMethodStr:tmpSafeSubToStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubToStr newMethodStr:tmpSafePointSubToStr];

        // 替换 substringWithRange:
        NSString *tmpSubRangeStr = @"substringWithRange:";
        NSString *tmpSafeSubRangeStr = @"safe_substringWithRange:";
        NSString *tmpSafePointSubRangeStr = @"safePoint_substringWithRange:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpSubRangeStr newMethodStr:tmpSafeSubRangeStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpSubRangeStr newMethodStr:tmpSafePointSubRangeStr];

        // 替换 rangeOfString:options:range:locale:
        NSString *tmpRangeOfStr = @"rangeOfString:options:range:locale:";
        NSString *tmpSafeRangeOfStr = @"safe_rangeOfString:options:range:locale:";
        NSString *tmpSafePointRangeOfStr = @"safePoint_rangeOfString:options:range:locale:";

        [self exchangeImplementationWithClassStr:@"__NSCFConstantString" originalMethodStr:tmpRangeOfStr newMethodStr:tmpSafeRangeOfStr];

        [self exchangeImplementationWithClassStr:@"NSTaggedPointerString" originalMethodStr:tmpRangeOfStr newMethodStr:tmpSafePointRangeOfStr];

    });
}

实现方法:

pragma mark --- implement method

/****************************************  substringFromIndex:  ***********************************/
  /**
 从from位置截取字符串 对应 __NSCFConstantString

 @param from 截取起始位置
 @return 截取的子字符串
 */
- (NSString *)safe_substringFromIndex:(NSUInteger)from {
    if (from > self.length ) {
        return nil;
    }
    return [self safe_substringFromIndex:from];
}
/**
 从from位置截取字符串 对应  NSTaggedPointerString

 @param from 截取起始位置
 @return 截取的子字符串
 */
- (NSString *)safePoint_substringFromIndex:(NSUInteger)from {
    if (from > self.length ) {
        return nil;
    }
    return [self safePoint_substringFromIndex:from];
}

/****************************************  substringFromIndex:  ***********************************/
 /**
 从开始截取到to位置的字符串  对应  __NSCFConstantString

 @param to 截取终点位置
 @return 返回截取的字符串
 */
- (NSString *)safe_substringToIndex:(NSUInteger)to   {
    if (to > self.length ) {
        return nil;
    }
    return [self safe_substringToIndex:to];
}

/**
 从开始截取到to位置的字符串  对应  NSTaggedPointerString

 @param to 截取终点位置
 @return 返回截取的字符串
 */
  - (NSString *)safePoint_substringToIndex:(NSUInteger)to {
    if (to > self.length ) {
        return nil;
    }
    return [self safePoint_substringToIndex:to];
}

/*********************************** rangeOfString:options:range:locale:  ***************************/
/**
 搜索指定 字符串  对应  __NSCFConstantString

 @param searchString 指定 字符串
 @param mask 比较模式
 @param rangeOfReceiverToSearch 搜索 范围
 @param locale 本地化
 @return 返回搜索到的字符串 范围
 */
- (NSRange)safe_rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale {
    if (!searchString) {
        searchString = self;
    }

    if (rangeOfReceiverToSearch.location > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if (rangeOfReceiverToSearch.length > self.length) {
         rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if ((rangeOfReceiverToSearch.location + rangeOfReceiverToSearch.length) > self.length) {
         rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    return [self safe_rangeOfString:searchString options:mask range:rangeOfReceiverToSearch locale:locale];
}

/**
 搜索指定 字符串  对应  NSTaggedPointerString

 @param searchString 指定 字符串
 @param mask 比较模式
 @param rangeOfReceiverToSearch 搜索 范围
 @param locale 本地化
 @return 返回搜索到的字符串 范围
 */
- (NSRange)safePoint_rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale {
    if (!searchString) {
        searchString = self;
    }

    if (rangeOfReceiverToSearch.location > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if (rangeOfReceiverToSearch.length > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if ((rangeOfReceiverToSearch.location + rangeOfReceiverToSearch.length) > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    return [self safePoint_rangeOfString:searchString options:mask range:rangeOfReceiverToSearch locale:locale];
}

/*********************************** substringWithRange:  ***************************/
/**
 截取指定范围的字符串  对应  __NSCFConstantString

 @param range 指定的范围
 @return 返回截取的字符串
 */
- (NSString *)safe_substringWithRange:(NSRange)range {
   if (range.location > self.length) {
        return nil;
    }

    if (range.length > self.length) {
        return nil;
    }

    if ((range.location + range.length) > self.length) {
        return nil;
    }
    return [self safe_substringWithRange:range];
}

/**
 截取指定范围的字符串 对应  NSTaggedPointerString

 @param range 指定的范围
 @return 返回截取的字符串
 */
- (NSString *)safePoint_substringWithRange:(NSRange)range {
    if (range.location > self.length) {
        return nil;
    }

    if (range.length > self.length) {
        return nil;
    }

    if ((range.location + range.length) > self.length) {
        return nil;
    }
    return [self safePoint_substringWithRange:range];
}

4.NSMutableString

主要替换方法:substringFromIndex:,substringToIndex:,substringWithRange:,rangeOfString:options:range:locale:,appendString,这几个主要方法

+ (void)load {
    //只执行一次这个方法
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        // 替换  substringFromIndex:
        NSString *tmpSubFromStr = @"substringFromIndex:";
        NSString *tmpSafeSubFromStr = @"safeMutable_substringFromIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFString" originalMethodStr:tmpSubFromStr newMethodStr:tmpSafeSubFromStr];

        // 替换  substringToIndex:
        NSString *tmpSubToStr = @"substringToIndex:";
        NSString *tmpSafeSubToStr = @"safeMutable_substringToIndex:";

        [self exchangeImplementationWithClassStr:@"__NSCFString" originalMethodStr:tmpSubToStr newMethodStr:tmpSafeSubToStr];

        // 替换  substringWithRange:
       NSString *tmpSubRangeStr = @"substringWithRange:";
        NSString *tmpSafeSubRangeStr = @"safeMutable_substringWithRange:";

        [self exchangeImplementationWithClassStr:@"__NSCFString" originalMethodStr:tmpSubRangeStr newMethodStr:tmpSafeSubRangeStr];

        // 替换  rangeOfString:options:range:locale:
        NSString *tmpRangeOfStr = @"rangeOfString:options:range:locale:";
        NSString *tmpSafeRangeOfStr = @"safeMutable_rangeOfString:options:range:locale:";

        [self exchangeImplementationWithClassStr:@"__NSCFString" originalMethodStr:tmpRangeOfStr newMethodStr:tmpSafeRangeOfStr];

        // 替换  appendString
        NSString *tmpAppendStr = @"appendString:";
        NSString *tmpSafeAppendStr = @"safeMutable_appendString:";

        [self exchangeImplementationWithClassStr:@"__NSCFString" originalMethodStr:tmpAppendStr newMethodStr:tmpSafeAppendStr];

    });
 }

实现方法:

pragma mark --- implement method

/****************************************  substringFromIndex:  ***********************************/
/**
 从from位置截取字符串 对应 __NSCFString

 @param from 截取起始位置
 @return 截取的子字符串
 */
- (NSString *)safeMutable_substringFromIndex:(NSUInteger)from {
    if (from > self.length ) {
        return nil;
    }
    return [self safeMutable_substringFromIndex:from];
}

/****************************************  substringFromIndex:  ***********************************/
/**
 从开始截取到to位置的字符串  对应  __NSCFString

 @param to 截取终点位置
 @return 返回截取的字符串
 */
- (NSString *)safeMutable_substringToIndex:(NSUInteger)to {
    if (to > self.length ) {
        return nil;
    }
    return [self safeMutable_substringToIndex:to];
}

/*********************************** rangeOfString:options:range:locale:  ***************************/
/**
 搜索指定 字符串  对应  __NSCFString

 @param searchString 指定 字符串
 @param mask 比较模式
 @param rangeOfReceiverToSearch 搜索 范围
 @param locale 本地化
 @return 返回搜索到的字符串 范围
 */
- (NSRange)safeMutable_rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale {
    if (!searchString) {
        searchString = self;
    }

    if (rangeOfReceiverToSearch.location > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if (rangeOfReceiverToSearch.length > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    if ((rangeOfReceiverToSearch.location + rangeOfReceiverToSearch.length) > self.length) {
        rangeOfReceiverToSearch = NSMakeRange(0, self.length);
    }

    return [self safeMutable_rangeOfString:searchString options:mask range:rangeOfReceiverToSearch locale:locale];
}

/*********************************** substringWithRange:  ***************************/
/**
 截取指定范围的字符串  对应  __NSCFString

 @param range 指定的范围
 @return 返回截取的字符串
 */
- (NSString *)safeMutable_substringWithRange:(NSRange)range {
    if (range.location > self.length) {
        return nil;
    }

    if (range.length > self.length) {
        return nil;
    }

    if ((range.location + range.length) > self.length) {
        return nil;
    }
    return [self safeMutable_substringWithRange:range];
}

/*********************************** safeMutable_appendString:  ***************************/
/**
 追加字符串 对应  __NSCFString

 @param aString 追加的字符串
 */
- (void)safeMutable_appendString:(NSString *)aString {
    if (!aString) {
        return;
    }
    return [self safeMutable_appendString:aString];
}

5.NSMutableDictionary

主要替换removeObjectForKey:和 setObject:forKey:这两个方法

  • (void)load { //只执行一次这个方法 static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{

        // 替换 removeObjectForKey:
        NSString *tmpRemoveStr = @"removeObjectForKey:";
        NSString *tmpSafeRemoveStr = @"safeMutable_removeObjectForKey:";
    
        [self exchangeImplementationWithClassStr:@"__NSDictionaryM" originalMethodStr:tmpRemoveStr newMethodStr:tmpSafeRemoveStr];
    
        // 替换 setObject:forKey:
        NSString *tmpSetStr = @"setObject:forKey:";
        NSString *tmpSafeSetRemoveStr = @"safeMutable_setObject:forKey:";
    
        [self exchangeImplementationWithClassStr:@"__NSDictionaryM" originalMethodStr:tmpSetStr newMethodStr:tmpSafeSetRemoveStr];
    });

    }

实现方法:

pragma mark --- implement method

/**
 根据akey 移除 对应的 键值对

 @param aKey key
 */
- (void)safeMutable_removeObjectForKey:(id<NSCopying>)aKey {
    if (!aKey) {
        return;
    }
    [self safeMutable_removeObjectForKey:aKey];
}

/**
 将键值对 添加 到 NSMutableDictionary 内

 @param anObject 值
 @param aKey 键
 */
- (void)safeMutable_setObject:(id)anObject forKey:(id<NSCopying>)aKey {
    if (!anObject) {
        return;
    }
    if (!aKey) {
        return;
    }
    return [self safeMutable_setObject:anObject forKey:aKey];
}

四:最后

这是gitHub链接地址:FJ_Safe,大家有兴趣可以看一下,如果觉得不错,麻烦给个喜欢或star,若发现问题请及时反馈,谢谢!

送上一张喜欢的图片: 排球少年.jpg -- 2017,新的开始!

原文作者: 林大鹏天地(简书作者)

原文链接:http://www.jianshu.com/p/bea2bfed3f3f

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