尝试取消封送映射[优先级]字符串

Question

我一直在玩 Golang json 包，并且遇到了一个问题，我只是想用最简单的方法将map[string]string解组map[Priority]string，但似乎我的 UnmarshalJSON 甚至没有运行，以下是我的代码，我想做一个可以运行的游乐场， 但我使用的是操作系统包，因此：

import (
    "encoding/json"
    "fmt"
    "os"
)
type Priority int
const (
    VERYLOW = Priority(iota)
    LOW
    MEDIUM
    HIGH
    VERYHIGH
)
const (
    verylow  = "verylow"
    low      = "low"
    medium   = "medium"
    high     = "high"
    veryhigh = "veryhigh"
    // ANSI color constants.
    RESET      = "x1b[0m"
    BRIGHT     = "x1b[1m"
    DIM        = "x1b[2m"
    UNDERSCORE = "x1b[4m"
    BLINK      = "x1b[5m"
    REVERSE    = "x1b[7m"
    HIDDEN     = "x1b[8m"
    FGBLACK    = "x1b[30m"
    FGRED      = "x1b[31m"
    FGGREEN    = "x1b[32m"
    FGYELLOW   = "x1b[33m"
    FGBLUE     = "x1b[34m"
    FGMAGENTA  = "x1b[35m"
    FGCYAN     = "x1b[36m"
    FGWHITE    = "x1b[37m"
    BGBLACK    = "x1b[40m"
    BGRED      = "x1b[41m"
    BGGREEN    = "x1b[42m"
    BGYELLOW   = "x1b[43m"
    BGBLUE     = "x1b[44m"
    BGMAGENTA  = "x1b[45m"
    BGCYAN     = "x1b[46m"
    BGWHITE    = "x1b[47m"
    TITLE_COLOUR = BRIGHT + FGGREEN
    NUMBER_COLOR = FGGREEN
    //color constants
    BLACK         = "BLACK"
    RED           = "RED"
    GREEN         = "GREEN"
    YELLOW        = "YELLOW"
    BLUE          = "BLUE"
    MAGENTA       = "MAGENTA"
    CYAN          = "CYAN"
    WHITE         = "WHITE"
    BRIGHTBLACK   = "BRIGHTBLACK"
    BRIGHTRED     = "BRIGHTRED"
    BRIGHTGREEN   = "BRIGHTGREEN"
    BRIGHTYELLOW  = "BRIGHTYELLOW"
    BRIGHTBLUE    = "BRIGHTBLUE"
    BRIGHTMAGENTA = "BRIGHTMAGENTA"
    BRIGHTCYAN    = "BRIGHTCYAN"
    BRIGHTWHITE   = "BRIGHTWHITE"
    NOCOLOR       = ""
)
type Config struct {
    Name     string
    FGColors map[Priority]string
}
type MarshalableConfig struct {
    Name     string
    FGColors map[string]string
}
var priorityMapFromString = map[string]Priority{
    veryhigh: VERYHIGH,
    high:     HIGH,
    medium:   MEDIUM,
    low:      LOW,
    verylow:  VERYLOW,
}
var priorityToString = map[Priority]string{
    VERYHIGH: veryhigh,
    HIGH:     high,
    MEDIUM:   medium,
    VERYLOW:  verylow,
    LOW:      low,
}
func (p Priority) String() string {
    return priorityToString[p]
}
func PriorityFromString(priority string) Priority {
    if p, ok := priorityMapFromString[priority]; ok {
        return p
    }
    return MEDIUM
}
func (priority *Priority) UnmarshalJSON(data []byte) error {
    var s string
    if err := json.Unmarshal(data, &s); err != nil {
        return err
    }
    *priority = PriorityFromString(s)
    return nil
}
func main() {
    fgColors := map[string]string{
        verylow:  RED,
        low:      BLUE,
        medium:   GREEN,
        high:     BRIGHTBLUE,
        veryhigh: BRIGHTMAGENTA,
    }
    m := MarshalableConfig{"Alice", fgColors}
    b, err := json.Marshal(m)
    if err != nil {
        panic(err)
    }
    file, err := os.Create("testfile.json")
    if err != nil {
        panic(err)
    }
    file.Write(b)
    emptyConfig := Config{}
    err = json.Unmarshal(b, &emptyConfig)
    if err != nil {
        fmt.Printf("Got a error from unmarshalling: %+v n", err)
        panic(err)
    }
    fmt.Printf("%+v n", emptyConfig)
    var x interface{} = emptyConfig.FGColors[VERYHIGH]
    fmt.Println(x.(string))
}

我收到错误：

json: cannot unmarshal number high into Go value of type main.Priority  

所以我得到的印象是它从不对优先级调用我的 UnmarshalJSON 方法，而且我不知道这是否是它应该工作的方式，因为我已经将优先级类型嵌套在地图中。

所以我也许必须为整个地图做一个别名类型，例如：

type FGColor map[Priority]string 

并在此基础上实现 Unmarshal，但这似乎不合逻辑，因为我认为嵌套结构将是 Unmarshal 的噩梦。

我做错了什么？？

Answer 1

正如AniSkywalker和putu在评论中提到的，你可以暗示encoding.TextUnmarshaler。

但是，我认为在您的情况下，由于您需要将Priority用作 json 映射键，因此仅将优先级用作类型字符串要容易得多。

type Priority string
const (
    VERYLOW = "verylow"
    LOW = "low"
    MEDIUM = "medium"
    HIGH = "high"
    VERYHIGH = "veryhigh" )

这样，您也可以放弃使用以下方法。

const (
    verylow  = "verylow"
    low      = "low"
    medium   = "medium"
    high     = "high"
    veryhigh = "veryhigh"
)

Answer 2

我根据 @AniSkywalker 到以下代码的注释，使用 UnmarshalText 更新了我的代码：

package main
import (
    "encoding/json"
    "fmt"
)
type Priority int
const (
    VERYLOW = Priority(iota)
    LOW
    MEDIUM
    HIGH
    VERYHIGH
)
const (
    verylow  = "verylow"
    low      = "low"
    medium   = "medium"
    high     = "high"
    veryhigh = "veryhigh"
    // ANSI color constants.
    RESET      = "x1b[0m"
    BRIGHT     = "x1b[1m"
    DIM        = "x1b[2m"
    UNDERSCORE = "x1b[4m"
    BLINK      = "x1b[5m"
    REVERSE    = "x1b[7m"
    HIDDEN     = "x1b[8m"
    FGBLACK    = "x1b[30m"
    FGRED      = "x1b[31m"
    FGGREEN    = "x1b[32m"
    FGYELLOW   = "x1b[33m"
    FGBLUE     = "x1b[34m"
    FGMAGENTA  = "x1b[35m"
    FGCYAN     = "x1b[36m"
    FGWHITE    = "x1b[37m"
    BGBLACK    = "x1b[40m"
    BGRED      = "x1b[41m"
    BGGREEN    = "x1b[42m"
    BGYELLOW   = "x1b[43m"
    BGBLUE     = "x1b[44m"
    BGMAGENTA  = "x1b[45m"
    BGCYAN     = "x1b[46m"
    BGWHITE    = "x1b[47m"
    TITLE_COLOUR = BRIGHT + FGGREEN
    NUMBER_COLOR = FGGREEN
    //color constants
    BLACK         = "BLACK"
    RED           = "RED"
    GREEN         = "GREEN"
    YELLOW        = "YELLOW"
    BLUE          = "BLUE"
    MAGENTA       = "MAGENTA"
    CYAN          = "CYAN"
    WHITE         = "WHITE"
    BRIGHTBLACK   = "BRIGHTBLACK"
    BRIGHTRED     = "BRIGHTRED"
    BRIGHTGREEN   = "BRIGHTGREEN"
    BRIGHTYELLOW  = "BRIGHTYELLOW"
    BRIGHTBLUE    = "BRIGHTBLUE"
    BRIGHTMAGENTA = "BRIGHTMAGENTA"
    BRIGHTCYAN    = "BRIGHTCYAN"
    BRIGHTWHITE   = "BRIGHTWHITE"
    NOCOLOR       = ""
)
type Config struct {
    Name     string
    FGColors map[Priority]string
}
type MarshalableConfig struct {
    Name     string
    FGColors map[string]string
}
var priorityMapFromString = map[string]Priority{
    veryhigh: VERYHIGH,
    high:     HIGH,
    medium:   MEDIUM,
    low:      LOW,
    verylow:  VERYLOW,
}
var priorityToString = map[Priority]string{
    VERYHIGH: veryhigh,
    HIGH:     high,
    MEDIUM:   medium,
    VERYLOW:  verylow,
    LOW:      low,
}
func (p Priority) String() string {
    return priorityToString[p]
}
func PriorityFromString(priority string) Priority {
    if p, ok := priorityMapFromString[priority]; ok {
        return p
    }
    return MEDIUM
}
func (priority *Priority) UnmarshalText(data []byte) error {
    *priority = PriorityFromString(string(data))
    return nil
}
func main() {
    fgColors := map[string]string{
        verylow:  RED,
        low:      BLUE,
        medium:   GREEN,
        high:     BRIGHTBLUE,
        veryhigh: BRIGHTMAGENTA,
    }
    m := MarshalableConfig{"Alice", fgColors}
    b, err := json.Marshal(m)
    if err != nil {
        panic(err)
    }
    emptyConfig := Config{}
    err = json.Unmarshal(b, &emptyConfig)
    if err != nil {
        fmt.Printf("Got a error from unmarshalling: %+v n", err)
        panic(err)
    }
    fmt.Printf("%+v n", emptyConfig)
    var x interface{} = emptyConfig.FGColors[VERYHIGH]
    fmt.Println(x.(string))
}