Dart 单例的四种写法

Dart汇总请点击这里

dart中的单例

工厂构造 Factory constructor

class Singleton{
    Singleton._privateConstructor();static final Singleton _instance = Singleton._privateConstructor();factory Singleton(){
    return _instance;}}void main() {
    Singleton s = Singleton();
}

静态变量 Static field with getter

class Singleton{
    Singleton._privateConstructor();static final Singleton _instance = Singleton._privateConstructor();static Singleton get instance {
     return _instance;}}void main() {
    Singleton s = Singleton.instance;
}

静态变量Static field

class Singleton {
    Singleton._privateConstructor();static final Singleton instance = Singleton._privateConstructor();}void main() {
    Singleton s = Singleton.instance;
}

常量和工厂构造 const constructor & factory

class Singleton {
    factory Singleton() =>const Singleton._internal_();const Singleton._internal_();
}void main() {
    print(new Singleton() == new Singleton());print(identical(new Singleton() , new Singleton()));
}