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我们先来看看有可能会出现的数组越界Crash的地方；
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- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { WelfareItem *item = [_datasourceArray objectAtIndex:indexPath.row];//有可能会越界，你在下拉刷新时会用[_datasourceArray removeAllObjects]，这时你又点了某个cell就会Crash}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { WelfareItem *item = _datasourceArray[indexPath.row];//有可能会越界，两个地方用了[tableView reloadData]；后一个有[_datasourceArray removeAllObjects]；前一个还没有执行完，就会Crash} |
上面代码是有可能会越界的；出现Crash也不好复现，发出去的App总是能收到几条Crash；解决这个问题也很简单代码如下：
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- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { WelfareItem *item = nil; if (indexPath.row < [_datasourceArray count]) {//无论你武功有多高，有时也会忘记加 item = [_datasourceArray objectAtIndex:indexPath.row]; }}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { WelfareItem *item = nil; if (indexPath.row < [_datasourceArray count]) { item = [_datasourceArray objectAtIndex:indexPath.row]; }} |
问题又来了，无论你武功有多高，有时也会忘记加；所以我们要想一招制敌办法；我是想到了用Runtime把objectAtIndex方法替换一下；代码如下：
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/*! @category @abstract NSObject的Category */@interface NSObject (Util)/*!@method swizzleMethod:withMethod:error:@abstract 对实例方法进行替换@param oldSelector 想要替换的方法@param newSelector 实际替换为的方法@param error 替换过程中出现的错误，如果没有错误为nil*/+ (BOOL)swizzleMethod:(SEL)originalSelector withMethod:(SEL)swizzledSelector error:(NSError **)error;@end#import "NSObject+Util.h"#import <objc runtime.h="">@implementation NSObject (Util)+ (BOOL)swizzleMethod:(SEL)originalSelector withMethod:(SEL)swizzledSelector error:(NSError **)error{ Method originalMethod = class_getInstanceMethod(self, originalSelector); if (!originalMethod) { NSString *string = [NSString stringWithFormat:@" %@ 类没有找到 %@ 方法",NSStringFromClass([self class]),NSStringFromSelector(originalSelector)]; *error = [NSError errorWithDomain:@"NSCocoaErrorDomain" code:-1 userInfo:[NSDictionary dictionaryWithObject:string forKey:NSLocalizedDescriptionKey]]; return NO; } Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector); if (!swizzledMethod) { NSString *string = [NSString stringWithFormat:@" %@ 类没有找到 %@ 方法",NSStringFromClass([self class]),NSStringFromSelector(swizzledSelector)]; *error = [NSError errorWithDomain:@"NSCocoaErrorDomain" code:-1 userInfo:[NSDictionary dictionaryWithObject:string forKey:NSLocalizedDescriptionKey]]; return NO; } if (class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) { class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod)); } else { method_exchangeImplementations(originalMethod, swizzledMethod); } return YES;}@end@implementation NSArray (ErrerManager)+ (void)load{ static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ @autoreleasepool { [objc_getClass("__NSArrayI") swizzleMethod:@selector(objectAtIndex:) withMethod:@selector(swizzleObjectAtIndex:) error:nil]; [objc_getClass("__NSArrayM") swizzleMethod:@selector(objectAtIndex:) withMethod:@selector(swizzleObjectAtIndex:) error:nil]; }; });}- (id)swizzleObjectAtIndex:(NSUInteger)index{ if (index < self.count) { return [self swizzleObjectAtIndex:index]; } NSLog(@"%@ 越界",self); return nil;//越界返回为nil}@end</objc> |
有了上面代码我们用 [_datasourceArray objectAtIndex:indexPath.row] 就不会发生越界Crash了；越界
了会返回nil；看来是一个比较不错的解决方案；把app发出去吧，结果我们Crash比之前高了好几倍（越界的Crash没有了，出新的Crash了）；Crash如下
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1 tbreader 0x002b93e9 tbreader + 20981532 libsystem_platform.dylib 0x33a66873 _sigtramp + 343 libsystem_blocks.dylib 0x33941ae1 _Block_release + 2164 libobjc.A.dylib 0x333c11a9 + 4045 CoreFoundation 0x25ba23a9 _CFAutoreleasePoolPop + 166 UIKit 0x2912317f + 427 CoreFoundation 0x25c565cd + 208 CoreFoundation 0x25c53c8b + 2789 CoreFoundation 0x25c54093 + 91410 CoreFoundation 0x25ba2621 CFRunLoopRunSpecific + 47611 CoreFoundation 0x25ba2433 CFRunLoopRunInMode + 10612 GraphicsServices 0x2cf0a0a9 GSEventRunModal + 13613 UIKit 0x2918c809 UIApplicationMain + 1440 |
都是这个Crash，出现在iOS7以上（含iOS7），关键还没有用户反馈有问题，Crash高了几倍没有一个用户反馈这种情况还是少见的，大家测试还复现不了；测试了一周终于复现了一样的Crash；是这样出现的，替换了objectAtIndex方法有输入的地方出来了软键盘按手机Home键就Crash了；此法不行只，只能另寻他策了。后来我们就给数组新增扩展方法代码如下
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@interface NSArray (SHYUtil)/*! @method objectAtIndexCheck: @abstract 检查是否越界和NSNull如果是返回nil @result 返回对象 */- (id)objectAtIndexCheck:(NSUInteger)index;@end#import "NSArray+SHYUtil.h"@implementation NSArray (SHYUtil)- (id)objectAtIndexCheck:(NSUInteger)index{ if (index >= [self count]) { return nil; } id value = [self objectAtIndex:index]; if (value == [NSNull null]) { return nil; } return value;}@end |
把之前的代码 WelfareItem *item = [_datasourceArray objectAtIndex:indexPath.row] 改为 WelfareItem *item = [_datasourceArray objectAtIndexCheck:indexPath.row] 就可以了。这样就可以彻底解决数组越界 -[__NSArrayI objectAtIndex:]: index 100 beyond bounds [0 .. 1]‘ 错误了
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原文地址：http://www.cnblogs.com/chglog/p/5322946.html
