iOS学习——第二天

第一部分＋－

+方法[类名 函数名]

-方法[实例 函数名]

//Test.h

#import <Foundation/Foundation.h>

@interface Test : NSObject

-(void)test:(int)a;//“－”代表实例方法（instance）

+(void)test2:(int)b;//"+"代表静态方法

@end

//Test.m

#import "Test.h"

@implementation Test

-(void)test:(int)a 

{

    NSLog(@"-");

}

+(void)test2:(int)b

{

    NSLog(@"+");

}

@end

//AppDelegate.h

#import "AppDelegate.h"

#import "Test.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    [Test test2:2];//静态方法可直接调用

    Test *t=[[Test alloc]init];//实例方法需要先实例化

    [t test:2];

     return YES;

}

Output:

第二部分  方法重载

//Parent.h

#import<Foundation/Foundation.h>

@ineterface Parent :NSObject

-(void)fun:(int)num;

@property (retain,nonatomic) NSMutableString *a;//retain相当于人工retain加1

@end

//Parent.m

#import"Parent.h"

@implementation Parent

-(void)fun:(int)num

{

   NSLog(@"I'm parent");

}

@end

//Child.h

#import"Parent.h"

@interface Child :Parent

-(void)fun:(int)num;

@end

//Child.m

#import"Child.h"

@implementation Child

-(void)fun:(int)num

{

   NSLog(@"I'm child");

}

@end

//AppDelegate.m

#import"AppDelegate.h"

#import"Parent.h"

#import"Child.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

   // Override point for customization after application launch.

    Parent *p1=[[Child alloc]init];

    [p1 fun:3];

@end

//这个.m并不完整，只纪录了改动的部分。.h没有改动

output:

第三部分 引用计数(non-ARC手工释放)

方法：点工程名－PROJECT／TARGETS－搜“automatic”－Object-c Automatic Reference Co…./Objective-C Automatic Reference Co….的选项选为“NO”

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

   // Override point for customization after application launch.

    Parent *p1=[[Child alloc]init];

    [p1 fun:3];

    NSString *tests=@"tests";

    p1.a=[NSMutableStringstringWithFormat:@"%@",tests];

   int count=[p1.aretainCount];//获得引用计数的值，当retainCount＝＝0时，释放内存

    NSLog(@"%d",count);

    [p1.aretain];//调用retain后，引用计数加1

    count=[p1.aretainCount];

    NSLog(@"%d",count);

    [p1.arelease];//调用release后，引用计数减1

    count=[p1.aretainCount];

    NSLog(@"%d",count);

@end

output:

有“retain”时@property (retain,nonatomic) NSMutableString *a;//retain相当于人工retain加1

无“retain”时@property (nonatomic) NSMutableString *a;

//如果把NSMutableString改为NSString，或者赋一个常量，则引用计数(retainCount)始终为－1或很大的数（与机器有关），这是因为程序运行时分为代码区和数据区等，在数据区里有常量区，只有当应用程序退出时才释放