Golang implements factory mode

Go language is a very popular statically compiled language. Its unique syntax and features make it very suitable for application in many scenarios. Among them, the factory pattern is one of the very common design patterns in the Go language. This article will introduce how to implement the factory pattern in Go language.

1. Introduction to Factory Pattern

Factory pattern is a common creation pattern. It defines an interface for creating objects and lets subclasses decide which objects to instantiate. a class. The factory pattern can separate the creation and use of objects, thereby improving the scalability and maintainability of the code.

Factory pattern often has two implementation methods: simple factory pattern and factory method pattern. The simple factory pattern generates all required objects from a factory class. It returns the corresponding objects by judging the type of the incoming parameters. The factory method pattern defines an interface for creating objects and lets subclasses decide which classes need to be instantiated.

2. Simple Factory Pattern Implementation

Let’s first look at the implementation of a simple factory pattern. Suppose we have a shape interface (Shape), which has a method (Draw) for drawing shapes. We hope to generate different shape objects, such as Circle and Rectangle, based on the different parameters passed in.

First we define a shape interface:

type Shape interface {
    Draw() string
}

Then we define two shape objects - circle and rectangle:

type Circle struct {}

func (c *Circle) Draw() string {
    return "draw circle"
}

type Rectangle struct {}

func (r *Rectangle) Draw() string {
    return "draw rectangle"
}

Finally we define a factory class (ShapeFactory) , to generate different shape objects based on the different parameters passed in:

type ShapeFactory struct {}

func (sf *ShapeFactory) CreateShape(shapeType string) Shape {
    switch shapeType {
        case "circle":
            return &Circle{}
        case "rectangle":
            return &Rectangle{}
        default:
            panic("wrong shape type")
    }
}

One thing to note here is that the factory class needs to return a shape interface, not a specific shape object. This avoids unnecessary dependence on the user of the specific type of the return value.

The following is a code example using a simple factory pattern:

sf := &ShapeFactory{}
circle := sf.CreateShape("circle")
fmt.Println(circle.Draw()) // 输出：draw circle

rectangle := sf.CreateShape("rectangle")
fmt.Println(rectangle.Draw()) // 输出：draw rectangle

3. Factory method pattern implementation

Next let’s look at a factory method pattern accomplish. Still taking shapes as an example, we change the original shape interface to a shape factory interface (ShapeFactoryInterface), which defines a method (CreateShape) for creating shape objects:

type ShapeFactoryInterface interface {
    CreateShape() Shape
}

Then we define two Shape factory - Circle Factory (CircleFactory) and Rectangle Factory (RectangleFactory). They all implement the shape factory interface, which is used to create corresponding shape objects:

type CircleFactory struct {}

func (cf *CircleFactory) CreateShape() Shape {
    return &Circle{}
}

type RectangleFactory struct {}

func (rf *RectangleFactory) CreateShape() Shape {
    return &Rectangle{}
}

As you can see, each shape has a corresponding factory, which is used to create instances of the shape. In this way, we can create different shape objects very flexibly without having to worry about coupling issues between different shape objects.

Finally, let’s look at a complete code example for creating factory objects of different shapes:

cf := &CircleFactory{}
circle := cf.CreateShape()
fmt.Println(circle.Draw()) // 输出：draw circle

rf := &RectangleFactory{}
rectangle := rf.CreateShape()
fmt.Println(rectangle.Draw()) // 输出：draw rectangle

4. Summary

That’s it, we Two ways to implement the factory pattern in Go language have been introduced: simple factory pattern and factory method pattern. In practical applications, we can choose the appropriate implementation method based on specific needs and scenarios.

The factory pattern can greatly improve the scalability and maintainability of the code, especially in scenarios where objects need to be created frequently. Therefore, it is very necessary for Go language developers to master the application method of factory pattern.

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