在Objective C中动态调用类方法 [英] Dynamically invoke a class method in Objective C

问题描述

假设我有Objective C接口 SomeClass ，它有一个类方法 someMethod ：

Suppose I have Objective C interface SomeClass which has a class method called someMethod:

@interface SomeClass : NSObject {
}

+ (id)someMethod;
@end

在一些其他接口中，我想有一个动态调用的帮助方法 someMethod 这样的类：

[someOtherObject invokeSelector:@selector(someMethod) forClass:[SomeClass class];

invokeSelector 的实现应该是什么？

What should be the implementation for invokeSelector? Is it possible at all?

- (void)invokeSelector:(SEL)aSelector forClass:(Class)aClass {
   // ???
}

推荐答案

>

Instead of:

[someOtherObject invokeSelector:@selector(someMethod) forClass:[SomeClass class];

调用：

[[SomeClass class] performSelector:@selector(someMethod)];

示例（使用GNUstep ...）

Example (using GNUstep ...)

文件Ah

#import <Foundation/Foundation.h>
@interface A : NSObject {}

- (NSString *)description;
+ (NSString *)action;
@end

文件Am

#import <Foundation/Foundation.h>
#import "A.h"

@implementation A

- (NSString *)description
{
    return [NSString stringWithString: @"A"];
}

+ (NSString *)action
{
    return [NSString stringWithString:@"A::action"];
}

@end

其他地方：

A *a = [[A class] performSelector:@selector(action)];
NSLog(@"%@",a);

输出：

2009-11-22 23:32:41.974 abc[3200] A::action

< hr>

来自 http://www.cocoabuilder.com/archive/cocoa/197631-how-do-classes-respond-to-performselector.html ：

在Objective-C中，类对象获取
根类的所有实例方法，这意味着从NSObject派生的每个类对象
获得所有NSObject的实例方法 -
包括performSelector：。

"In Objective-C, a class object gets all the instance methods of the root class for its hierarchy. This means that every class object that descends from NSObject gets all of NSObject's instance methods - including performSelector:."

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