Go中int、float、string的相互轉換

引用

// 推薦一個更加強大的轉換庫：https://github.com/spf13/cast
package main

import (
    "fmt"
    "strconv"
)

func main() { 

 // 測試 int 和 string(decimal) 互相轉換的函數 // https://yourbasic.org/golang/convert-int-to-string/
    // int -> string
    sint := strconv.Itoa(97)
    fmt.Println(sint, sint == "97")

    // byte -> string
    bytea := byte(1)
    bint := strconv.Itoa(int(bytea))
    fmt.Println(bint)

    // int64 -> string
    sint64 := strconv.FormatInt(int64(97), 10)
    fmt.Println(sint64, sint64 == "97")

    // int64 -> string (hex) ，十六進制
    sint64hex := strconv.FormatInt(int64(97), 16)
    fmt.Println(sint64hex, sint64hex == "61")

    // string -> int
    _int, _ := strconv.Atoi("97")
    fmt.Println(_int, _int == int(97))

    // string -> int64
    _int64, _ := strconv.ParseInt("97", 10, 64)
    fmt.Println(_int64, _int64 == int64(97))

    // https://stackoverflow.com/questions/30299649/parse-string-to-specific-type-of-int-int8-int16-int32-int64
    // string -> int32，注意 parseInt 始終返回的是 int64，所以還是需要 int32(n) 強轉一下
    _int32, _ := strconv.ParseInt("97", 10, 32)
    fmt.Println(_int32, int32(_int32) == int32(97))

    // int32 -> string, https://stackoverflow.com/questions/39442167/convert-int32-to-string-in-golang
    fmt.Println("------- int32 -> string ------")
   res1 := strconv.FormatInt(int64(23), 10) // fast
    fmt.Println("res1>>> ",res1)
    res2 := strconv.Itoa(int(23)) // fast
    fmt.Println("res2>>> ",res2)
    res3 := fmt.Sprint(23) // slow
    fmt.Println("re3s>>> ",res3)
    fmt.Println("-------------")
    // int -> int64 ，不會丟失精度
    var n int = 97
    fmt.Println(int64(n) == int64(97))

    // string -> float32/float64 https://yourbasic.org/golang/convert-string-to-float/
    f := "3.14159265"
    if s, err := strconv.ParseFloat(f, 32); err == nil {
        fmt.Println(s) // 3.1415927410125732
    }
    if s, err := strconv.ParseFloat(f, 64); err == nil {
        fmt.Println(s) // 3.14159265
    }

    // float -> string https://yourbasic.org/golang/convert-string-to-float/
    s := fmt.Sprintf("%f", 123.456)
    fmt.Println("s>>> ",s)
}

另外一個轉換庫

https://github.com/spf13/cast