iOS-Runtime之数组越界

来源:互联网 时间:2017-01-22


关于数组越界目前大概有两种方式,一种是通过分类添加安全的索引方法,第二种就是Runtime实现,第一种如果是个人开发比较建议,如果是团队开发很难得到保证和推动,关于Runtime处理数组越界网上有人说是在iOS7及以上有软键盘输入的地方按Home键退出,会出现崩溃,测试过两台手机iOS8.1和iOS9.3暂时没有出现问题,如果之后出现问题会更新文章.


方法交换

Runtime解决数据越界及字典key或value为nil的情况,主要通过Runtime的方法交换实现,可以扩展一下NSObject分类:


@implementation NSObject (FlyElephant)
- (void)swizzleMethod:(SEL)originalSelector swizzledSelector:(SEL)swizzledSelector{
Class class = [self class];
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
BOOL didAddMethod = class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
@end

现在需要扩展NSArray和NSDictionary分类,实现方法交换:
@implementation NSArray (FlyElephant)
+ (void)load{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
@autoreleasepool {
[objc_getClass("__NSArray0") swizzleMethod:@selector(objectAtIndex:) swizzledSelector:@selector(emptyObjectIndex:)];
[objc_getClass("__NSArrayI") swizzleMethod:@selector(objectAtIndex:) swizzledSelector:@selector(arrObjectIndex:)];
[objc_getClass("__NSArrayM") swizzleMethod:@selector(objectAtIndex:) swizzledSelector:@selector(mutableObjectIndex:)];
[objc_getClass("__NSArrayM") swizzleMethod:@selector(insertObject:atIndex:) swizzledSelector:@selector(mutableInsertObject:atIndex:)];
}
});
}
- (id)emptyObjectIndex:(NSInteger)index{
return nil;
}
- (id)arrObjectIndex:(NSInteger)index{
if (index >= self.count || index < 0) {
return nil;
}
return [self arrObjectIndex:index];
}
- (id)mutableObjectIndex:(NSInteger)index{
if (index >= self.count || index < 0) {
return nil;
}
return [self mutableObjectIndex:index];
}
- (void)mutableInsertObject:(id)object atIndex:(NSUInteger)index{
if (object) {
[self mutableInsertObject:object atIndex:index];
}
}
@end
@implementation NSDictionary (FlyElephant)
+ (void)load{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
@autoreleasepool {
[objc_getClass("__NSDictionaryM") swizzleMethod:@selector(setObject:forKey:) swizzledSelector:@selector(mutableSetObject:forKey:)];
}
});
}
- (void)mutableSetObject:(id)obj forKey:(NSString *)key{
if (obj && key) {
[self mutableSetObject:obj forKey:key];
}
}
@end

注意NSArray0表示一般空数组,NSArrayI表示一般数组,__NSArrayM可变数组,NSArray和NSMutableArray相当于工厂,最终实现通过上面三个类进行实现的,有兴趣的可以自行了解一下类簇.


测试

测试代码:


NSArray *emptyArr = [NSArray new];
NSLog(@"%@",[emptyArr objectAtIndex:10]);
NSArray *arr = @[@"FlyElephant",@"keso"];
NSString *result = [arr objectAtIndex:10];
NSLog(@"%@",result);
NSMutableArray *mutableArr = [[NSMutableArray alloc] initWithArray:arr];
NSLog(@"%@", mutableArr[100]);
NSString *obj;
[mutableArr addObject:obj];
//NSDictionary
NSString *dictValue;
NSMutableDictionary *mutableDict = [NSMutableDictionary dictionary];
[mutableDict setValue:dictValue forKey:@"FlyElephant"];
[mutableDict setObject:dictValue forKey:dictValue];
NSLog(@"%@",mutableDict);

2016.08.17更新
昨天测试的时候还没有问题,今天早上运行项目发现一个莫名其妙的问题:


**[UIKeyboardLayoutStar release]: message sent to deallocated instance 0x1459e0600**

通过Runtime进行对数组字典进行方法交换之后,之前对键盘输入的场景没有完全弄清楚,完整过程应该是,文本框输入文字→Home键进入后台→点击App图标重新进入→崩溃,有的时候前两步就直接崩溃了,因此Runtime的这个文件需要通过mrc管理:
一般项目都是 ARC 模式,需要单独问Runtime的这个问题添加MRC支持,
Build Phases -> Compile Sources找到文件设置 -fno-objc-arc 标签。
如果项目是MRC 模式,则为 ARC 模式的代码文件加入 -fobjc-arc 标签.
同时可以为相应的代码块添加autoreleasepool:
@autoreleasepool {
if (index >= self.count || index < 0) {
return nil;
}
return [self arrObjectIndex:index];
}



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