FJ_Safe

FJ_Safe简书链接

支持pod操作

NSString、NSArray、NSMutableString、NSMutableArray、NSMutableDictionary通过运行时直接给原生的插入、删除、截取等操作添加判断，防止崩溃。

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。

Class Clusters（类簇）是抽象工厂模式在iOS下的一种实现，它是接口简单性和扩展性的权衡体现，在我们完全不知情的情况下，偷偷隐藏了很多具体的实现类， 只暴露出简单的接口。 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,所以替换系统中相应的类型对应的原生方法必须根据他实际实现类。

以NSString为例:

经研究发现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/runtime.h>
#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

经过下面测试代码，进行测试:

// __NSCFConstantString 类型
NSString *tmpConstantString = @"432423432432432432";
[tmpConstantString substringFromIndex:10000];
[tmpConstantString substringToIndex:1000];
[tmpConstantString substringWithRange:NSMakeRange(100, 10000)];
[tmpConstantString rangeOfString:nil];

// NSTaggedPointerString 类型
NSString *tmpPointerString = [NSString stringWithFormat:@"4"];
[tmpPointerString substringFromIndex:10000];
[tmpPointerString substringToIndex:1000];
[tmpPointerString substringWithRange:NSMakeRange(100, 10000)];
[tmpPointerString rangeOfString:nil];

// __NSCFString 类型(备注:类似这样:[NSString stringWithFormat:@"4535435435435"]出来也是__NSCFString,因为NSMutableString初始化出来都是__NSCFString类型，所以归到NSMutableString里面)
NSMutableString *tmpCFString = [NSMutableString stringWithFormat:@"4535435435435"];
[tmpCFString substringFromIndex:10000];
[tmpCFString substringToIndex:1000];
[tmpCFString substringWithRange:NSMakeRange(100, 10000)];
[tmpCFString rangeOfString:nil];
[tmpCFString appendString:nil];

// __NSArray0 类型
NSArray *tmpZoroArray = [NSArray array];
tmpZoroArray[100];
[tmpZoroArray objectAtIndex:1000];

// __NSSingleObjectArrayI 类型
NSArray *tmpSingleObjectArray = [NSArray arrayWithObject:@"200"];
tmpSingleObjectArray[100];
[tmpSingleObjectArray objectAtIndex:1000];

// __NSArrayI 类型
NSArray *tmpArrayI = [NSArray arrayWithObjects:@"1",@"2", nil];
tmpArrayI[100];
[tmpArrayI objectAtIndex:1000];

// __NSArrayM 类型
NSMutableArray *tmpMutableArrayM = [NSMutableArray arrayWithCapacity:0];
[tmpMutableArrayM objectAtIndex:1000];
[tmpMutableArrayM insertObject:nil atIndex:10000];
[tmpMutableArrayM removeObject:nil];
[tmpMutableArrayM removeObjectAtIndex:1000];
[tmpMutableArrayM removeObjectsInRange:NSMakeRange(-100, 10000)];


// __NSDictionaryM 类型
NSMutableDictionary *tmpMutableDictM = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"100",@"A",@"200",@"B", nil];
[tmpMutableDictM removeObjectForKey:nil];
[tmpMutableDictM setObject:nil forKey:@"C"];
[tmpMutableDictM setObject:@"300" forKey:nil];

像这几种操作都不会导致崩溃。

   若有不足，麻烦您指出，谢谢！