respondsToSelector的相关使用

 

• 
  
  • -(BOOL) isKindOfClass: classObj 用来判断是否是某个类或其子类的实例
  • -(BOOL) isMemberOfClass: classObj 用来判断是否是某个类的实例
  • -(BOOL) respondsToSelector: selector 用来判断是否有以某个名字命名的方法(被封装在一个selector的对象里传递)
  • +(BOOL) instancesRespondToSelector: selector 用来判断实例是否有以某个名字命名的方法. 和上面一个不同之处在于, 前面这个方法可以用在实例和类上，而此方法只能用在类上.
  • -(id) performSelector: selector

    SEL sel = @selector (start:) ; // 指定action  

    if ([obj respondsToSelector:sel]) 

    { //判断该对象是否有相应的方法  

    [obj performSelector:sel withObject:self]; //调用选择器方法  

    } 

    使用[[UIApplication sharedApplication] keyWindow]查找应用程序的主窗口对象

    respondsToSelector判断是否实现了某方法

    Tester.h

    

    #import <Foundation/Foundation.h>
    
    
    @interface Tester : NSObject {
    
    }
    
    -(void) test:(NSString*) msg;
    
    -(void) notImp;
    
    @end

    

    Tester.m

    

    #import "Tester.h"
    
    @implementation Tester
    
    -(void) test:(NSString*) msg
    {
    NSLog(@"%@", msg);
    }
    
    @end

    

    注意：没有实现notImp方法

    main.m

    

    #import <Foundation/Foundation.h>
    #import "Tester.h"
    
    int main (int argc, const char * argv[])
    {
    
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    id tester = [[Tester alloc] init];//注意，这里使用id
    
    SEL testSelector = @selector(test:);
    SEL notImpSelector = @selector(notImp:);
    
    if([tester respondsToSelector:testSelector])
    {
    //tester.m中实现了test方法
    [tester test:@"invoke test method"];
    }
    if([tester respondsToSelector:notImpSelector])
    {
    //test.m中没有实现此主就去
    [tester notImp];
    }
    
    
    [pool drain];
    return 0;
    }

    

     

     

     

     

    1. #import <UIKit/UIKit.h>  
    2.    
    3. @interface ViewController : UIViewController{  
    4.     UIButton *btn1;  
    5.     UIButton *btn2;  
    6.      
    7.     UILabel *label1;  
    8. }  
    9.    
    10. -(void)testRespond1;  
    11. -(void)notTest;  
    12.    
    13. @end  
    14.    
    15.    
    16. #import "ViewController.h"  
    17.    
    18. @implementation ViewController  
    19.    
    20. - (void)didReceiveMemoryWarning  
    21. {  
    22.     [super didReceiveMemoryWarning];  
    23.     // Release any cached data,images, etc that aren't in use.  
    24. }  
    25.    
    26. #pragma mark - View lifecycle  
    27.    
    28. - (void)viewDidLoad  
    29. {  
    30.     [super viewDidLoad];  
    31.          // Do any additional setupafter loading the view, typically from a nib.  
    32.      
    33.     btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];  
    34.     btn1.frame = CGRectMake(50, 100, 100, 50);  
    35.     [btn1 setTitle:@"BTN1" forState:UIControlStateNormal];  
    36.     [btn1 addTarget:self action:@selector(btn1Clicked:) forControlEvents:UIControlEventTouchUpInside];  
    37.     [self.view addSubview:btn1];  
    38.      
    39.     btn2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];  
    40.     btn2.frame = CGRectMake(200, 100, 100, 50);  
    41.     [btn2 setTitle:@"BTN2" forState:UIControlStateNormal];  
    42.     [btn2 addTarget:self action:@selector(btn2Clicked:) forControlEvents:UIControlEventTouchUpInside];  
    43.     [self.view addSubview:btn2];  
    44. }  
    45.    
    46. -(void)btn1Clicked:(id)sender  
    47. {  
    48.     if ([self respondsToSelector:@selector(testRespond1)])  
    49.     {  
    50.        [self testRespond1];  
    51.     }  
    52. }  
    53.    
    54. -(void)btn2Clicked:(id)sender  
    55. {  
    56.     if (![self respondsToSelector:@selector(notTest)])  
    57.     {  
    58.        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"notTest 没有被实现" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];  
    59.         [alert show];  
    60.         [alert release];  
    61.     }  
    62. }  
    63.    
    64. -(void)testRespond1  
    65. {  
    66.     label1 = [[UILabel alloc] initWithFrame:CGRectMake(50, 200, 220, 200)];  
    67.     label1.text = @"testRespond1 被实现了";  
    68.     [self.view addSubview:label1];  
    69.     [label1 release];  
    70. }  
    71.    
    72. - (void)viewDidUnload  
    73. {  
    74.     [super viewDidUnload];  
    75.     //Release any retained subviews of the main view.  
    76.     // e.g.self.myOutlet = nil;  
    77. }  
    78.    
    79. -(void)dealloc  
    80. {  
    81.     [super dealloc];  
    82. }  
    83.    
    84. @end  

Tester.h

#import <Foundation/Foundation.h>


@interface Tester : NSObject {

}

-(void) test:(NSString*) msg;

-(void) notImp;

@end

Tester.m

#import "Tester.h"

@implementation Tester

-(void) test:(NSString*) msg
{
NSLog(@"%@", msg);
}

@end

注意：没有实现notImp方法

main.m

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

int main (int argc, const char * argv[])
{

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

id tester = [[Tester alloc] init];//注意，这里使用id

SEL testSelector = @selector(test:);
SEL notImpSelector = @selector(notImp:);

if([tester respondsToSelector:testSelector])
{
//tester.m中实现了test方法
[tester test:@"invoke test method"];
}
if([tester respondsToSelector:notImpSelector])
{
//test.m中没有实现此主就去
[tester notImp];
}


[pool drain];
return 0;
}

 

 

 

 

1. #import <UIKit/UIKit.h>  
2.    
3. @interface ViewController : UIViewController{  
4.     UIButton *btn1;  
5.     UIButton *btn2;  
6.      
7.     UILabel *label1;  
8. }  
9.    
10. -(void)testRespond1;  
11. -(void)notTest;  
12.    
13. @end  
14.    
15.    
16. #import "ViewController.h"  
17.    
18. @implementation ViewController  
19.    
20. - (void)didReceiveMemoryWarning  
21. {  
22.     [super didReceiveMemoryWarning];  
23.     // Release any cached data,images, etc that aren't in use.  
24. }  
25.    
26. #pragma mark - View lifecycle  
27.    
28. - (void)viewDidLoad  
29. {  
30.     [super viewDidLoad];  
31.          // Do any additional setupafter loading the view, typically from a nib.  
32.      
33.     btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];  
34.     btn1.frame = CGRectMake(50, 100, 100, 50);  
35.     [btn1 setTitle:@"BTN1" forState:UIControlStateNormal];  
36.     [btn1 addTarget:self action:@selector(btn1Clicked:) forControlEvents:UIControlEventTouchUpInside];  
37.     [self.view addSubview:btn1];  
38.      
39.     btn2 = [UIButton buttonWithType:UIButtonTypeRoundedRect];  
40.     btn2.frame = CGRectMake(200, 100, 100, 50);  
41.     [btn2 setTitle:@"BTN2" forState:UIControlStateNormal];  
42.     [btn2 addTarget:self action:@selector(btn2Clicked:) forControlEvents:UIControlEventTouchUpInside];  
43.     [self.view addSubview:btn2];  
44. }  
45.    
46. -(void)btn1Clicked:(id)sender  
47. {  
48.     if ([self respondsToSelector:@selector(testRespond1)])  
49.     {  
50.        [self testRespond1];  
51.     }  
52. }  
53.    
54. -(void)btn2Clicked:(id)sender  
55. {  
56.     if (![self respondsToSelector:@selector(notTest)])  
57.     {  
58.        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"notTest 没有被实现" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];  
59.         [alert show];  
60.         [alert release];  
61.     }  
62. }  
63.    
64. -(void)testRespond1  
65. {  
66.     label1 = [[UILabel alloc] initWithFrame:CGRectMake(50, 200, 220, 200)];  
67.     label1.text = @"testRespond1 被实现了";  
68.     [self.view addSubview:label1];  
69.     [label1 release];  
70. }  
71.    
72. - (void)viewDidUnload  
73. {  
74.     [super viewDidUnload];  
75.     //Release any retained subviews of the main view.  
76.     // e.g.self.myOutlet = nil;  
77. }  
78.    
79. -(void)dealloc  
80. {  
81.     [super dealloc];  
82. }  
83.    
84. @end