[消息传递之三]－NSInvocation练习

- (void)viewDidLoad {
[super viewDidLoad];
id m = [[MyInvoc alloc] init];
SEL s = @selector(myLen:);
NSMethodSignature* sign = [MyInvoc instanceMethodSignatureForSelector:s];
NSInvocation* n = [NSInvocation invocationWithMethodSignature:sign];
[n setTarget:m];
[n setSelector:s];
NSString* w = @"hello world";
[n setArgument:&w atIndex:2];
[n invoke];
NSInteger r ;
[n getReturnValue:&r];
NSLog(@"length is %ld",r);
// NSLog(@"name is %@, length is %ld",[m name], [m length]);
}

1，nsinvocation能传递多个参数，并且能获取返回值，这两点比performselector;withobject要强大。

2，需要配合方法签名使用，幸好这个获取签名的函数在nsobject里面就有～

3，在哪个线程调用，就用哪个线程执行，貌似没有延迟执行方法，这个与performselector有差别～