iphone - 类扩展 - 无法识别的二传手

Question

以下代码崩溃了:

@interface AppDelegate (PrivateMethods)

@property (nonatomic, strong) NSString * name;

@end

@implementation AppDelegate

- (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    self.name = @"foobar";
    ...

错误是:

'-[AppDelegate setName:]: unrecognized selector sent to instance 0x6d73df0'

当我改变的时候

@interface AppDelegate (PrivateMethods)

到

@interface AppDelegate ()

那么就可以了，请问是什么原因呢？

更新:如下所述，由于我必须为此目的使用类扩展，现在这个问题变成了:使用类扩展来声明私有(private)方法是否可以接受？

例如

@interface AppDelegate ()

- (void) start;
@property (nonatomic, strong) NSString * name;

@end

Answer 1

类扩展基本上用于增强公共(public)属性变量。假设你已经暴露了只读对象，或者任何变量的getter方法，那么你在扩展中创建了与readwrite相同的对象。而Category仅用于增强类的方法/功能。

检查这个

@interface MyClass : NSObject
// property here is used as readonly.
@property (retain, readonly) float value;
@end

// Private extension, typically hidden in the main implementation file.
@interface MyClass ()
@property (retain, readwrite) float value;
@end

或

@interface MyClass : NSObject
// here we have exposed getter method of private instance.
- (float) value;
@end

// Private extension, typically hidden in the main implementation file.
@interface MyClass ()
@property (retain, strong) float value;
@end