使用方法和属性有什么区别？
我正在研究“The Elements”示例应用程序的源代码，我在 AtomicElement.h 有四个属性声明为只读：
@property (readonly) UIImage *stateImageForAtomicElementTileView;
@property (readonly) UIImage *flipperImageForAtomicElementNavigationItem;
@property (readonly) UIImage *stateImageForAtomicElementView;
@property (readonly) CGPoint positionForElement;
在实现文件中，它们看起来像
- (UIImage *)stateImageForAtomicElementTileView {
return [UIImage imageNamed:[NSString stringWithFormat:@"%@_37.png",state]];
}
您可以详细说明这样做的原因吗那？为什么不使用类似
- (UIImage*) stateImageForAtomicElementTileView;
头文件中的内容，然后像 [element stateImageForAtomicElementTileView]; 而不是 element.stateImageForAtomicElementTileView 那样访问它？
I am studying the source code for "The Elements" sample app and I see that in AtomicElement.h there are four properties declared as readonly:
@property (readonly) UIImage *stateImageForAtomicElementTileView;
@property (readonly) UIImage *flipperImageForAtomicElementNavigationItem;
@property (readonly) UIImage *stateImageForAtomicElementView;
@property (readonly) CGPoint positionForElement;
In the implementation file, they look like
- (UIImage *)stateImageForAtomicElementTileView {
return [UIImage imageNamed:[NSString stringWithFormat:@"%@_37.png",state]];
}
Can you please elaborate on the reasons to do that? Why not use something like
- (UIImage*) stateImageForAtomicElementTileView;
in the header file, and then access it like [element stateImageForAtomicElementTileView]; instead of element.stateImageForAtomicElementTileView?
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评论（1）
我认为没有技术原因来选择一种习语而不是另一种，它们都可以以相同的方式使用。这更多是一个语义问题。
类既具有数据又可以执行操作（通常对所述数据）。我认为您应该考虑使用属性，并使用
.访问而不是[ ]更多地作为记录stateImageForAtomicElementTileView。它是属于类的一部分的图像（事实上不是从资源动态生成的，应该被视为实现细节）
I don't think there's a technical reason to choose one idiom over the other, they can both be used in the same way. It's more a matter of semantics.
A class has both data and can perform operations (usually on said data). I think you should look at using a property, and having the
.access instead of[ ]more as a way of documenting the purpose of thestateImageForAtomicElementTileView.It's an image that's part of the class (the fact is't being generated on the fly from a resource should be seen as an implementation detail)