IOS NSInvocation用法
2013-10-24 13:52
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原文地址 http://www.cnblogs.com/csj007523/archive/2012/07/25/2608432.html
main.h
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#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
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#import <Foundation/Foundation.h>
@interface MyClass : NSObject {
}
- (NSString *)appendMyString:(NSString *)string;
@end
MyClass.m
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#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
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
[html] view
plaincopy
#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
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plaincopy
#import <Foundation/Foundation.h>
@interface MyClass : NSObject {
}
- (NSString *)appendMyString:(NSString *)string;
@end
MyClass.m
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plaincopy
#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
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