为什么只读属性设置器是工作目标c [英] why readonly property setter is working objective c

问题描述

@interface ViewController : UIViewController{
    NSNumber *nmbr;

}
@property (nonatomic, readonly) NSNumber *nmbr;
- (NSNumber*)nmbr;
- (void)setNmbr:(NSNumber *)value;
@end

---

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setNmbr:[NSNumber numberWithInt:4]];
    NSLog(@"Value of number is: %@", self.nmbr);

}

- (NSNumber*)nmbr{
    return nmbr;
}

- (void)setNmbr:(NSNumber *)value{
    nmbr = value;
}

@end

我希望程序不要让setNmbr函数起作用，因为接口文件中的nmbr属性是只读的.但这是在设置nmbr的值.我在做什么错?

I am expecting the program not to let setNmbr function work because nmbr property in the interface file is readonly. But it is setting the value of nmbr. What wrong am I doing?

推荐答案

readonly不会阻止您编写自己的设置器.它只是阻止编译器为您合成设置器.如果您为readonly属性实现了设置器，但它会警告您，那会很好，但事实并非如此.

The readonly doesn't prevent you from writing your own setter. It simply prevents the compiler from synthesizing a setter for you. It would be nice if it warned you if you implemented a setter for a readonly property, but it doesn't.

很显然，不建议为readonly属性实现一个setter.此外，您通常甚至都不会声明该ivar也不会实现该属性的getter，因为它们都将为您合成(除非您在那里做一些特别的事情，否则就不是).

Clearly, it's inadvisable to implement a setter for a readonly property. Furthermore, you generally wouldn't even declare the ivar nor implement the getter for the property, either, because those would both be synthesized for you (unless you were doing something special there, which you're not).

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