one piece design

[xiao-ice]

one piece design

[hixb]

one piece design

`
export default class MyLocalStorage {
// Static properties and object properties are the two major members of a class
static localStorage: MyLocalStorage;

private constructor() {
console.log("This is the constructor of the static method of the singleton design pattern of ts");
}

// Provide a method for external access, through which this method is used to provide a method for external access to an object
// 1. A method with the static keyword is a static method
// 2. Static methods have nothing to do with objects, external object variables cannot call static methods and static properties
// 3. External can be called by class name
// Static methods cannot access instance properties or instance methods [object properties or object methods]
public static getInstance() {
// if the static property does not point to the created object
if (!this.localStorage) {
this.localStorage = new MyLocalStorage();
}
return this.localStorage;
}

public setItem(key: string, value: any) {
localStorage.setItem(key, JSON.stringify(value));
}

public getItem(key: string) {
const getLoginUser = localStorage.getItem(key);
return getLoginUser ? JSON.parse(getLoginUser) : null;
}
}

/**

• Build a single-piece design pattern
• 1. Set the constructor to be private, and do not allow external instances of the class to be created [object]
• 2. At least one external access method should be provided to get the property, and the external can get an object through this method or property, so this method should be set as a static method
• 3. Externally call the static method provided in the second step to obtain an object
     */
     `