摘要: Objective-C中调用函数的方法是消息传递，这个和普通的函数调用的区别是，你可以随时对一个对象传递任何消息，而不需要在编译的时候声明这些方法。所以Objective-C可以在runtime的时候传递人和消息。首先介绍两个方法。
Objective-C中调用函数的方法是“消息传递”，这个和普通的函数调用的区别是，你可以随时对一个对象传递任何消息，而不需要在编译的时候声明这些方法。所以Objective-C可以在runtime的时候传递人和消息。
首先介绍两个方法 SEL和@selector
根据AppleObjective-C Runtime Reference官方文档这个传递消息的函数就是 id objc_msgSend(id theReceiver, SEL theSelector, …)
theReceiver是接受消息的对象类型是id，theSelector是消息名称类型是SEL。下边代码我们来看看如何来生成一个SEL，如果传递消息。
- (void) fooNoInputs {
NSLog(@"Does nothing");
}
然后调用它
[self performSelector:@selector(fooNoInputs)];
第二个试验看看如何在消息中传递参数
我们建立一个有input参数的函数
- (void) fooOneIput:(NSString*) first {
NSLog(@"Logs %@", first);
}
然后调用它
[self performSelector:@selector(fooOneInput:) withObject:@"first"];
第三个试验更多的参数
- (void) fooFirstInput:(NSString*) first secondInput:(NSString*) second {
NSLog(@"Logs %@ then %@", first, second);
}
然后调用它
[self performSelector:@selector(fooFirstInput:secondInput:) withObject:@"first"withObject:@"second"];
第四个试验如何建立动态的函数，然后调用他们？我们需要建立一个selector
SEL myTestSelector = @selector(myTest:);
并且我们调用的函数在另外一个Class内
- (void)abcWithAAA: (NSNumber *)number {
int primaryKey = [number intValue];
NSLog("%i", primaryKey);
}
MethodForSelectors * mfs = [MethodForSelectors alloc];
NSArray *Arrays = [NSArray arrayWithObjects:@"AAA", @"BBB", nil];
for ( NSString *array in Arrays ){
SEL customSelector = NSSelectorFromString([NSStringstringWithFormat:@"abcWith%@:", array]);
mfs = [[MethodForSelectors alloc] performSelector:customSelector withObject:0];
}
完整的代码：
@implementation ClassForSelectors
- (void) fooNoInputs {NSLog(@"Does nothing");
}
- (void) fooOneIput:(NSString*) first {
NSLog(@"Logs %@", first);
}
- (void) fooFirstInput:(NSString*) first secondInput:(NSString*) second {
NSLog(@"Logs %@ then %@", first, second);
}
- (NSArray *)abcWithAAA: (NSNumber *)number {
int primaryKey = [number intValue];
NSLog("%i", primaryKey);
}
- (void) performMethodsViaSelectors {
[self performSelector:@selector(fooNoInputs)];
[self performSelector:@selector(fooOneInput:) withObject:@"first"];
[self performSelector:@selector(fooFirstInput:secondInput:) withObject:@"first"withObject:@"second"];
}
- (void) performDynamicMethodsViaSelectors {
MethodForSelectors * mfs = [MethodForSelectors alloc];
NSArray *Arrays = [NSArray arrayWithObjects:@"AAA", @"BBB", nil];
for ( NSString *array in Arrays ){
SEL customSelector = NSSelectorFromString([NSStringstringWithFormat:@"abcWith%@:", array]);
mfs = [[MethodForSelectors alloc] performSelector:customSelector withObject:0];
}
}
@end
@implementation MethodForSelectors- (void)abcWithAAA: (NSNumber *)number {
NSLog("%i", number);
}
@end