这个写法会出什么问题： @property (copy) NSMutableArray *array;

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用@property (copy) NSMutableArray *array;会有什么问题？

我们县回忆一下copy属性的作用,一个属性标记了copy,当你调用他的setter方法,他会建立一个索引计数为1的对象,然后释放旧对象. @property (copy) NSMutableArray * a; NSMutableArray* b = [NSMutableArray array]; a = b; 等同于 @property (strong) NSMutableArray * a; NSMutableArray* b = [NSMutableArray array]; a = [b…

这个写法会出什么问题： @property (copy) NSMutableArray *array;

因为copy策略拷贝出来的是一个不可变对象,然而却把它当成可变对象使用,很容易造成程序奔溃 //如:-[__NSArrayI removeObjectAtIndex:]: unrecognized selector sent to instance 0x7fcd1bc30460 // copy后返回的是不可变对象(即 arr 是 NSArray 类型,NSArray 类型对象不能调用 NSMutableArray 类型对象的方法) 这里还有一个问题,该属性使用了同步锁,会在创建时生成一些额外的代…

objective c, property, copy

@property (copy) nsmutablearray *array -copy, as implemented by mutable Cocoa classes, always returns their immutable counterparts. Thus, when an NSMutableArray is sent -copy, it returns an NSArray containing the same objects. http://stackoverflow.co…

使用asp.net MVC的 HtmlHelper 时遇到的小问题，报错:Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions.

异常信息:Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions 解决办法: 由以下代码: @foreach (var item in Model) { @Html.DisplayFor(m => !item.IsIdle, "BoolIcon") } 改为:…

ios 内存管理与property copy strong weak assign

- (void)fun{ NSString* str = [[NSString alloc] initWithString:@"string"]; NSLog(@"%d", [str retainCount]);}可以看到 str的计数器为-1 而把initWithString换成initWithFormat 计数器就是1 ------解决方案--------------------------------------------------------没有区别…

[Angular 2] Using a Reducer to Change an Object's Property Inside an Array

Reducers are also often used for changing a single property inside of other reducers. This lesson shows how a type can enter the people reducer, but then the people reducer can use a different type to call the clock reducer and get a value back. So t…