Introduction to the proxy pattern of JavaScript design patterns_javascript skills

Proxy mode description

Note: As the name suggests, one class is used to replace another class to perform method functions. This mode is somewhat similar to the decoration mode. The difference is that the proxy mode initializes the proxy object class on behalf of the client, while the decoration mode uses an interface or The initial decorator parameter reference is used to execute.

In dynamic object-oriented languages, the proxy mode not only controls and modifies the proxy class, but also fully hides and protects the proxy class; the proxy class is only indirectly initialized and called when we need it. ;

Scene description:

A very common example is the case of renting a house. The tenant wants to rent a house and the landlord wants to rent it out. However, neither the tenant nor the landlord has time to look for a house or wait for someone to look at the house at home, so they go to a housing agency together. . The landlord entrusts the room to an intermediary agent for renting and selling. When a suitable person is needed, the intermediary will show the room and pay for renting it. This will help the landlord rent out the room; the room entrusted by the tenant must meet the room location conditions required by the agent. After the agency helps the tenant find a shared room, the two pay to rent it, thus renting a place for the tenant;

Example source code

Follow the above example;

1. Landlord rental;

Copy code The code is as follows:

function Fangdong() {
This.room = 'Room name';
}
Fangdong.prototype.chuzu = function() {
console.log('The landlord rents the room: ' this.room);
}

2. Intermediary agent class:

Copy code The code is as follows:

function Proxy() {
This.fangdong = new Fangdong();
}

Proxy.prototype.chuzu = function() {
This.fangdong.chuzu();
console.log('Agency fee will be charged after renting out');
}

3. How to use:

Copy code The code is as follows:

//The tenant asks the agent to help find a house;
var proxy = new Proxy();
proxy.chuzu();

Look at the above usage, the proxy class is not needed at all on the client side, just use the Proxy class, which can be used very well in scenarios where certain business logic processes need to be protected; using the proxy mode, it can be easily Good protection requires protected proxy classes;

Other instructions

Similar to the decorator pattern, the proxy pattern also well embodies the principle of object-oriented thinking that is open to extension and closed to modification;
Proxy mode, you can use interfaces or abstract classes to standardize common interfaces: (JAVA proxy mode is provided below)

1. Abstract class abstract method;

Copy code The code is as follows:

public abstract class House {
Public void abstract chuzu();
}

public class Fangdong extends House {
Private String room = “Room name”;
@Override
Public void chuzu() {
System.out.println(room);
}
}

public class Proxy extends House {
Private Fangdong fangdong;
Public Proxy() {
This.fangdong = new Hangdong();
}
@Override
Public void chuzu() {
This.fandong.chuzu();
System.out.println("Pay the agency fee after renting");
}
}

//Use
House house = new Proxy();
house.chuzu();

2. Interface Interface mode:

Copy code The code is as follows:

interface House {
    public void chuzu();
}

public class Fangdong implements House {
    private String room = “房间名称”;
    @Override
    public void chuzu() {
        System.out.println(room);
    }
}

public class Proxy implements House {
    private Fangdong fangdong;
    public Proxy() {
        this.fangdong = new Hangdong();
    }
    @Override
    public void chuzu() {
        this.fandong.chuzu();
        System.out.println(“出租后交中介费”);
    }
}

//使用
House house = new Proxy();
house.chuzu();