How to implement an ordering system using Go language

This article will introduce how to use Go language to implement a simple and easy-to-understand order system.

1. Demand Analysis

We need a simple and easy-to-understand ordering system, which at least needs to implement the following functions:

1. Display and selection of products
2. Function of shopping cart
3. Generation and display of orders

Considering that our time and energy are limited, we will only implement a simple mall system, and we Only two items are available to choose from. The information of these two products is as follows:

Product name	Product price
Product 1	10 yuan
Product 2	20 yuan

We need Implement this mall system in the command line.

2. Code implementation

1. Create product structure

We first need to create a structure to store product information. The code example is as follows:

type product struct {
    name  string
    price int
}

var products = []product{
    {"商品1", 10},
    {"商品2", 20},
}

2. Product display

We need to implement a function to display product information. The code example is as follows:

func showProducts() {
    fmt.Println("== 商品列表 ==")
    for _, p := range products {
        fmt.Printf("%s %d元\n", p.name, p.price)
    }
    fmt.Println("================")
}

3. Shopping cart implementation

We need to implement a shopping cart structure to store the product information selected by the user. The code example is as follows:

type cart struct {
    items map[string]int
}

func newCart() *cart {
    return &cart{items: make(map[string]int)}
}

func (c *cart) addItem(name string, qty int) {
    c.items[name] += qty
}

func (c *cart) clear() {
    c.items = make(map[string]int)
}

func (c *cart) total() int {
    total := 0
    for name, qty := range c.items {
        for _, p := range products {
            if p.name == name {
                total += p.price * qty
                break
            }
        }
    }
    return total
}

func (c *cart) show() {
    if len(c.items) == 0 {
        fmt.Println("购物车为空")
        return
    }

    fmt.Println("== 购物车 ==")
    for name, qty := range c.items {
        fmt.Printf("%s × %d\n", name, qty)
    }
    fmt.Printf("总计 %d元\n", c.total())
    fmt.Println("============")
}

4. Order implementation

We need to implement An order function is to generate the product information in the shopping cart into an order. The code example is as follows:

func checkout(c *cart) {
    if len(c.items) == 0 {
        fmt.Println("购物车为空")
        return
    }

    // 生成订单
    order := make(map[string]int)
    for name, qty := range c.items {
        order[name] = qty
    }

    // 清空购物车
    c.clear()

    fmt.Println("== 订单详情 ==")
    for name, qty := range order {
        for _, p := range products {
            if p.name == name {
                fmt.Printf("%s × %d\n", name, qty)
                fmt.Printf("单价 %d元，总价 %d元\n", p.price, p.price*qty)
                break
            }
        }
    }
    fmt.Printf("总计 %d元\n", c.total())
    fmt.Println("============")
}

5. Command line interaction

We need to implement a command line interaction function , for users to select the product and quantity, and complete the order. The code example is as follows:

func interactive() {
    scanner := bufio.NewScanner(os.Stdin)
    c := newCart()

    for {
        showProducts()
        c.show()
        fmt.Print("请选择商品（输入商品编号）：")
        scanner.Scan()
        id := scanner.Text()
        if id == "q" {
            break
        }

        var p product
        for _, p = range products {
            if p.name == id {
                break
            }
        }
        if p.price == 0 {
            fmt.Printf("商品 %s 不存在\n", id)
            continue
        }

        fmt.Print("请输入数量：")
        scanner.Scan()
        qtyStr := scanner.Text()
        qty, err := strconv.Atoi(qtyStr)
        if err != nil {
            fmt.Println("输入的数量无效")
            continue
        }

        c.addItem(p.name, qty)
    }

    checkout(c)
}

3. The complete code

The complete code is as follows:

package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
)

type product struct {
    name  string
    price int
}

var products = []product{
    {"商品1", 10},
    {"商品2", 20},
}

type cart struct {
    items map[string]int
}

func newCart() *cart {
    return &cart{items: make(map[string]int)}
}

func (c *cart) addItem(name string, qty int) {
    c.items[name] += qty
}

func (c *cart) clear() {
    c.items = make(map[string]int)
}

func (c *cart) total() int {
    total := 0
    for name, qty := range c.items {
        for _, p := range products {
            if p.name == name {
                total += p.price * qty
                break
            }
        }
    }
    return total
}

func (c *cart) show() {
    if len(c.items) == 0 {
        fmt.Println("购物车为空")
        return
    }

    fmt.Println("== 购物车 ==")
    for name, qty := range c.items {
        fmt.Printf("%s × %d\n", name, qty)
    }
    fmt.Printf("总计 %d元\n", c.total())
    fmt.Println("============")
}

func showProducts() {
    fmt.Println("== 商品列表 ==")
    for _, p := range products {
        fmt.Printf("%s %d元\n", p.name, p.price)
    }
    fmt.Println("================")
}

func checkout(c *cart) {
    if len(c.items) == 0 {
        fmt.Println("购物车为空")
        return
    }

    // 生成订单
    order := make(map[string]int)
    for name, qty := range c.items {
        order[name] = qty
    }

    // 清空购物车
    c.clear()

    fmt.Println("== 订单详情 ==")
    for name, qty := range order {
        for _, p := range products {
            if p.name == name {
                fmt.Printf("%s × %d\n", name, qty)
                fmt.Printf("单价 %d元，总价 %d元\n", p.price, p.price*qty)
                break
            }
        }
    }
    fmt.Printf("总计 %d元\n", c.total())
    fmt.Println("============")
}

func interactive() {
    scanner := bufio.NewScanner(os.Stdin)
    c := newCart()

    for {
        showProducts()
        c.show()
        fmt.Print("请选择商品（输入商品编号）：")
        scanner.Scan()
        id := scanner.Text()
        if id == "q" {
            break
        }

        var p product
        for _, p = range products {
            if p.name == id {
                break
            }
        }
        if p.price == 0 {
            fmt.Printf("商品 %s 不存在\n", id)
            continue
        }

        fmt.Print("请输入数量：")
        scanner.Scan()
        qtyStr := scanner.Text()
        qty, err := strconv.Atoi(qtyStr)
        if err != nil {
            fmt.Println("输入的数量无效")
            continue
        }

        c.addItem(p.name, qty)
    }

    checkout(c)
}

func main() {
    interactive()
}

4. Summary

This article briefly introduces how to use Go language to implement a simple and easy-to-understand ordering system. By implementing functions such as product display, shopping cart function, and order generation and display, we have implemented a useful mall system with certain functions. Practicality and reference value. Before development, we need to fully understand the needs and goals so that we can better complete product development. At the same time, the efficiency and simplicity of the Go language also provide us with reliable and efficient development tools and support.

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