在Objective-C中，如何从类别访问私有财产 [英] in Objective-C, how to access private property from category

问题描述

我想从类别中访问类的私有属性。

I want to access private property of a class from its category.

但是要访问私有属性，我必须重新声明类别中的同一私有属性。 >
如果我没有重新声明，我收到编译错误，属性'< property name>'找不到'< class name>类型的对象*'。

But to access private property, I have to redeclare the same private property in category.
If I don't redeclare, I get a compile error, Property '<property name>' not found on object of type '<class name> *'.

这是从类别访问类私有财产的正确方法吗？

还有更好的方法要做到这一点？

Is this correct way to access private property of class from category?
And are there better ways to do this?

以下代码是私有财产在类别中重新申报的代码：

The following code is the code which private property is redeclared in category:

ClassA。 h

ClassA.h

@interface ClassA : NSObject
-(void)method1;
@end

ClassA.m

#import "ClassA.h"

// private property
@interface ClassA()
@property (nonatomic) NSString *s;
@end

@implementation ClassA
@synthesize s;

-(void)method1
{
    self.s = @"a";
    NSLog(@"%@", [NSString stringWithFormat:@"%@ - method1", self.s]);
}
@end

ClassA + Category.h

ClassA+Category.h

#import "ClassA.h"

@interface ClassA(Category)
-(void)method2;
@end

ClassA + Category.m

ClassA+Category.m

#import "ClassA+Category.h"

// redeclare private property
@interface ClassA()
@property(nonatomic) NSString *s;
@end

@implementation ClassA(Category)

-(void)method2
{
    NSLog(@"%@", [NSString stringWithFormat:@"%@ - method2", self.s]);
}
@end

为私有属性创建文件（ClassA + Private.m）并从ClassA.m和ClassA + Category.m导入它是一种好方法：

Is is good way to create a file(ClassA+Private.m) for private property and import it from ClassA.m and ClassA+Category.m:

ClassA + Private.m

ClassA+Private.m

@interface ClassA()
@property(nonatomic) NSString *s;
@end

推荐答案

解决方案的最佳方法这是创建 ClassA + Private.h 并将其导入 ClassA.m 和类别.M 。记住最后的 h ，你只需要在那里声明你的私有属性和方法，定义最好保存在 ClassA.m 。

The best way to solve this is to create ClassA+Private.h and import it in ClassA.m and Category.m. Mind the h at the end, you only need to declare your private properties and methods there, the definition is better kept in ClassA.m.

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