Go语言中interface{}类型转换的进阶实践与objx库应用

var data map[string]interface{}
jsonBytes := []byte(`{"s": "wow", "x":123, "y":true, "a":["a123", "a234"]}`)
err := json.Unmarshal(jsonBytes, &data)
if err != nil {
    // handle error
}

// 如何安全地获取 data["s"] 为 string, data["x"] 为 int, data["y"] 为 bool, data["a"] 为 []string?

func toBool(i1 interface{}) bool {
    if i1 == nil {
        return false
    }
    switch i2 := i1.(type) {
    case bool:
        return i2
    case string:
        // 考虑 "true" 字符串
        return i2 == "true"
    case int:
        // 考虑非零整数
        return i2 != 0
    case *bool:
        if i2 == nil { return false }
        return *i2
    case *string:
        if i2 == nil { return false }
        return *i2 == "true"
    case *int:
        if i2 == nil { return false }
        return *i2 != 0
    default:
        return false
    }
}

go get github.com/stretchr/objx

package main

import (
    "encoding/json"
    "fmt"
    "github.com/stretchr/objx"
)

func main() {
    var m1 map[string]interface{}
    jsonBytes := []byte(`{"s": "wow", "x":123, "y":true, "arr":["a123", "a234"], "f": 3.14}`)
    err := json.Unmarshal(jsonBytes, &m1)
    if err != nil {
        fmt.Printf("JSON unmarshal error: %v\n", err)
        return
    }

    // 将 map[string]interface{} 转换为 objx.Map
    o := objx.New(m1)

    // 使用Get方法获取值并进行类型转换
    s := o.Get("s").Str()
    x := o.Get("x").Int()
    y := o.Get("y").Bool()
    f := o.Get("f").Float64()

    fmt.Printf("s (string): %s (type: %T)\n", s, s) // wow (type: string)
    fmt.Printf("x (int): %d (type: %T)\n", x, x)   // 123 (type: int)
    fmt.Printf("y (bool): %t (type: %T)\n", y, y)  // true (type: bool)
    fmt.Printf("f (float64): %f (type: %T)\n", f, f) // 3.140000 (type: float64)

    // 处理数组类型
    arrValue := o.Get("arr")
    if arrValue.IsMSI() { // 检查是否是 []interface{}
        // 或者直接使用Strings()方法
        arr := arrValue.Strings()
        fmt.Printf("arr ([]string): %v (type: %T)\n", arr, arr) // [a123 a234] (type: []string)
    } else {
        fmt.Println("arr is not a slice of interfaces or cannot be converted to []string")
    }

    // 处理不存在的字段并提供默认值
    nonExistent := o.Get("non_existent").Str("default_value")
    fmt.Printf("nonExistent (string with default): %s\n", nonExistent) // default_value
}

package main

import (
    "fmt"
    "github.com/stretchr/objx"
)

func main() {
    // 使用 MustFromJSON 从 JSON 字符串创建 objx.Map
    m := objx.MustFromJSON(`{"name": "Mat", "age": 30, "city": "New York"}`)

    // 获取姓名和年龄
    name := m.Get("name").Str()
    age := m.Get("age").Int()

    fmt.Printf("Name: %s, Age: %d\n", name, age) // Name: Mat, Age: 30

    // 获取昵称，如果不存在则使用姓名作为默认值
    nickname := m.Get("nickname").Str(name)
    fmt.Printf("Nickname (with default): %s\n", nickname) // Nickname (with default): Mat

    // 获取一个可能不存在的字段，并提供默认值
    country := m.Get("country").Str("USA")
    fmt.Printf("Country (with default): %s\n", country) // Country (with default): USA
}