IOS开发之——单例-GCD实现(4)

发表于 分类于 ， ， 阅读时长 ≈ 2 分钟

一 概述

  • ARC模式下的GCD实现
  • 非ARC模式下的GCD实现

二 ARC模式下的GCD实现

2.1 如何确认ARC模式

TARGETS——Build Settings——搜索autom，找到Objective-C Automatic Reference Counting(YES)

main.m方法使用@autoreleasepool

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#import <UIKit/UIKit.h>
#import "AppDelegate.h"

int main(int argc, char * argv[]) {
    NSString * appDelegateClassName;
    @autoreleasepool {
        appDelegateClassName = NSStringFromClass([AppDelegate class]);
    }
    return UIApplicationMain(argc, argv, nil, appDelegateClassName);
}

2.2 ARC模式下的单例(NSDataTool)

NSDataTool.h

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#import <Foundation/Foundation.h>
@interface NSDataTool : NSObject
+(instancetype)shareDataTool;
@end

NSDataTool.m

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#import "NSDataTool.h"
@implementation NSDataTool
static id _instance;

+(instancetype)allocWithZone:(struct _NSZone *)zone
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance=[super allocWithZone:zone];
    });
    return _instance;
}
+(instancetype)shareDataTool
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance=[[self alloc]init];
    });
    return _instance;
}
-(id)copyWithZone:(NSZone *)zone
{
    return _instance;
}
@end

三 非ARC模式下的GCD实现

3.1 非ARC确认

TARGETS——Build Settings——搜索autom，找到Objective-C Automatic Reference Counting(NO)

main.m方法没有使用@autoreleasepool

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#import <UIKit/UIKit.h>
#import "AppDelegate.h"
int main(int argc, char * argv[]) {
    NSString * appDelegateClassName;

        appDelegateClassName = NSStringFromClass([AppDelegate class]);
  
    return UIApplicationMain(argc, argv, nil, appDelegateClassName);
}

3.2 非ARC出现的问题(调用release方法)

3.3 非ARC模式下的单例(NSDataTool)

NSDataTool.h

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#import <Foundation/Foundation.h>
@interface NSDataTool : NSObject
+(instancetype)shareDataTool;
@end

NSDataTool.m

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#import "NSDataTool.h"

@implementation NSDataTool

static id _instance;

+(instancetype)allocWithZone:(struct _NSZone *)zone
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance=[super allocWithZone:zone];
    });
    return _instance;
}

+(instancetype)shareDataTool
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance=[[self alloc]init];
    });
    return _instance;
}
-(id)copyWithZone:(NSZone *)zone
{
    return _instance;
}
//空方法
-(oneway void)release
{  
}
-(instancetype)retain
{
    return self;
}
- (NSUInteger)retainCount
{
    return 1;
}
@end

说明：

  • release：为空，不使用默认实现
  • retain：返回当前示例
  • retainCount：返回1