目录
什么是单例模式
最简单，最常用的设计模式之一，主要解决了一个全局使用的类频繁地创建与销毁。
当您想控制实例数目，节省系统资源的时候，就可以使用单例模式
1、全局唯一，只初始化一次，只有一个实例
2、只提供一个接口，私有化初始化接口
3、线程安全
4、最好能懒加载（不强求）
单例模式实现
一、实现
class Singleton: NSObject {
//存储类型属性在初始化时必须赋值，因为没有初始化器来初始化它，
//存储类型属性的赋值是线程安全的，由系统 保证
//let保证只赋值一次
//存储类型属性默认lazy只有再使用时才会初始化
//以上保证了可以实现单例模式
static let shared = Singleton()
//私有化初始化器
private override init() {
super.init()
}
}
二、唯一性测试
func test1() {
for _ in 0..<10 {
let sle = Singleton.shared
print(sle)
}
//调用初始化方法报错：Singleton' initializer is inaccessible due to 'private' protection level
//let sle = Singleton()
/**
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
<LCClientDemo.Singleton: 0x281690090>
*/
}
三、线程安全测试
func test2() {
for _ in 0...10 {
let thread = Thread.init {
let sle = Singleton.shared
print(Thread.current, sle)
}
thread.start()
}
}
/**
<NSThread: 0x2801c0340>{number = 8, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c15c0>{number = 9, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c1c80>{number = 10, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c09c0>{number = 11, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c0000>{number = 12, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c2080>{number = 14, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c5880>{number = 17, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c7f40>{number = 18, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c0c80>{number = 13, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c0940>{number = 15, name = (null)} <LCClientDemo.Singleton: 0x281690090>
<NSThread: 0x2801c1680>{number = 16, name = (null)} <LCClientDemo.Singleton: 0x281690090>
*/
单例应用
1、程序整个生命周期内有且只有一份
UIApplication.shared
2、管理工具类
UserDefaults.standard
FileManager.default
NotificationCenter.default
补充
一、OC的实现方式
static LCLoginMananger * manager = nil;
+(instancetype)shareInstance{
static dispatch_once_t onceToken;
//保证线程安全和一次执行
dispatch_once(&onceToken, ^{
manager = [[LCLoginMananger alloc] init];
manager.biometry = [[LCBiometryTool alloc] init];
[manager copyBundleToUserDefault];
});
return manager;
}
//保证alloc和new出的也是同一对象
//+(instancetype)alloc{
// if (!manager) {
// manager = [super alloc];
// }
// return manager;
//}
//保证allocWithZone出的也是同一个对象
//alloc会调用allocWithZone，所以重写了这个方法，上边的方法可以不重写
+(instancetype)allocWithZone:(struct _NSZone *)zone{
if (!manager){
manager = [super allocWithZone:zone];
}
return manager;
}
二、调用
-(void)sharedTest{
for (int i = 0; i<10; i++) {
NSThread * thread = [[NSThread alloc] initWithBlock:^{
LCLoginMananger * manger = [LCLoginMananger shareInstance];
NSLog(@"manager = %@,thread = %@",manger,[NSThread currentThread]);
}];
[thread start];
}
LCLoginMananger * manager0 = [[LCLoginMananger alloc] init];
NSLog(@"manager0 = %@",manager0);
LCLoginMananger * manager1 = [LCLoginMananger new];
NSLog(@"manager1 = %@",manager1);
LCLoginMananger * manager2 = [[LCLoginMananger allocWithZone:nil] init];
NSLog(@"manager2 = %@",manager2);
/**
manager0 = <LCLoginMananger: 0x2813f9a60>
manager1 = <LCLoginMananger: 0x2813f9a60>
manager2 = <LCLoginMananger: 0x2813f9a60>
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048d080>{number = 9, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048d0c0>{number = 10, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048cf40>{number = 11, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048d040>{number = 12, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048d000>{number = 13, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048cf80>{number = 15, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048cfc0>{number = 14, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048ce40>{number = 16, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048ce80>{number = 17, name = (null)}
manager = <LCLoginMananger: 0x2813f9a60>,thread = <NSThread: 0x28048d100>{number = 18, name = (null)}
*/
}
行者常至，为者常成！