IOS NSInvocation用法
在 iOS中可以直接调用 某个对象的消息 方式有2中 一种是performSelector:withObject: 再一种就是NSInvocation 第一种方式比较简单,能完成简单的调用。但是对于>2个的参数或者有返回值的处理,那就需要做些额外工作才能搞定。那么在这种情况下,我们就可以使用NSInvocation来进行这些相对复杂的操作 |
main.h
- #import <Foundation/Foundation.h>
- #import "MyClass.h"
- int main (int argc, const char * argv[])
- {
- NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
- MyClass *myClass = [[MyClass alloc] init];
- NSString *myString = @"My string";
- //普通调用
- NSString *normalInvokeString = [myClass appendMyString:myString];
- NSLog(@"The normal invoke string is: %@", normalInvokeString);
- //NSInvocation调用
- SEL mySelector = @selector(appendMyString:);
- NSMethodSignature * sig = [[myClass class]
- instanceMethodSignatureForSelector: mySelector];
- NSInvocation * myInvocation = [NSInvocation invocationWithMethodSignature: sig];
- [myInvocation setTarget: myClass];
- [myInvocation setSelector: mySelector];
- [myInvocation setArgument: &myString atIndex: 2];
- NSString * result = nil;
- [myInvocation retainArguments];
- [myInvocation invoke];
- [myInvocation getReturnValue: &result];
- NSLog(@"The NSInvocation invoke string is: %@", result);
- [myClass release];
- [pool drain];
- return 0;
- }
MyClass.h
- #import <Foundation/Foundation.h>
- @interface MyClass : NSObject {
- }
- - (NSString *)appendMyString:(NSString *)string;
- @end
MyClass.m
- #import "MyClass.h"
- @implementation MyClass
- - (id)init
- {
- self = [super init];
- if (self) {
- // Initialization code here.
- }
- return self;
- }
- - (NSString *)appendMyString:(NSString *)string
- {
- NSString *mString = [NSString stringWithFormat:@"%@ after append method", string];
- return mString;
- }
- - (void)dealloc
- {
- [super dealloc];
- }
- @end
这里说明一下[myInvocation setArgument: &myString atIndex: 2];为什么index从2开始 ,原因为:0 1 两个参数已经被target 和selector占用