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!