yaml：解组错误：无法将字符串解组为时间。Golang中的持续时间答案

【问题标题】：yaml: unmarshal errors: cannot unmarshal string into time.Duration in Golangyaml：解组错误：无法将字符串解组为时间。Golang中的持续时间
【发布时间】：2018-08-09 19:33:02
【问题描述】：

我的结构如下：

type Connect struct {
     ClientID string `yaml:"clientid"`
     Password string `yaml:"password"`
     Timeout  time.Duration `yaml:"timeout"`
}

c1 := `
    id: 'client1'
    password: 'hhhhhhha'
    timeout: 10
    `

c2 := `
    id: 'client2'
    password: 'llllllla'
    timeout: '10'
    `

c3 := `
    id: 'client3'
    password: 'hhhhhhha'
    timeout: 10s
    `

c4 := `
    id: 'client4'
    password: 'llllllla'
    timeout: '10s'
    `

如上图，Timeout的类型是time.Duration，默认单位是纳秒，但是我想得到结果：c1 && c2有错误，c3 && c4有效（Timeout的配置必须有单位）。我应该如何为 yaml 重写 UnmarshalYAML() 方法？非常感谢。

【问题讨论】：

标签： go yaml unmarshalling

【解决方案1】：

我将在UnmarshalYAML 函数中创建一个别名类型，以便将所有值解组为某些原始类型。然后我将重写那些匹配的值并转换那些不匹配的值：

package main

import (
    "fmt"
    "time"

    "gopkg.in/yaml.v2"
)

type Connect struct {
    ClientID string        `yaml:"clientid"`
    Password string        `yaml:"password"`
    Timeout  time.Duration `yaml:"timeout"`
}

func (ut *Connect) UnmarshalYAML(unmarshal func(interface{}) error) error {
    type alias struct {
        ClientID string `yaml:"clientid"`
        Password string `yaml:"password"`
        Timeout  string `yaml:"timeout"`
    }

    var tmp alias
    if err := unmarshal(&tmp); err != nil {
        return err
    }

    t, err := time.ParseDuration(tmp.Timeout)
    if err != nil {
        return fmt.Errorf("failed to parse '%s' to time.Duration: %v", tmp.Timeout, err)
    }

    ut.ClientID = tmp.ClientID
    ut.Password = tmp.Password
    ut.Timeout = t

    return nil
}

func main() {
    c1 := `
id: 'client1'
password: 'hhhhhhha'
timeout: 10
`

    c2 := `
id: 'client2'
password: 'llllllla'
timeout: '10'
`

    c3 := `
id: 'client3'
password: 'hhhhhhha'
timeout: 10s
`

    c4 := `
id: 'client4'
password: 'llllllla'
timeout: '10s'
`

    cc := []string{c1, c2, c3, c4}
    for i, cstr := range cc {
        var c Connect
        err := yaml.Unmarshal([]byte(cstr), &c)
        if err != nil {
            fmt.Printf("Error for c%d: %v\n", (i + 1), err)
            continue
        }
        fmt.Printf("c%d: %+v\n", (i + 1), c)
    }
}

输出如下：

$ go run main.go
Error for c1: failed to parse '10' to time.Duration: time: missing unit in duration10
Error for c2: failed to parse '10' to time.Duration: time: missing unit in duration10
c3: {ClientID: Password:hhhhhhha Timeout:10s}
c4: {ClientID: Password:llllllla Timeout:10s}

【讨论】：

【解决方案2】：

如果您无法在 Connect 的 UnmarshalYAML 方法中执行此操作，则一种方法是为实现 Unmarshaler 接口的 Timeout 创建自定义类型：

type Connect struct {
     ClientID string `yaml:"clientid"`
     Password string `yaml:"password"`
     Timeout  UnmarshalingTimeout `yaml:"timeout"`
}

type UnmarshalingTimeout time.Duration 

func (ut UnmarshalingTimeout) UnmarshalYAML(unmarshal func(interface{}) error) error {
    // implement unmarshaling here
}

【讨论】：

谢谢。但是当我编译时，它有另一个错误“不能使用 Connect.Timeout (type UnmarshalingTimeout) as type time.Duration in field value”
@kuailehaibin 不幸的是，您需要来回转换以用作 time.Duration，但很容易做到：time.Duration(Connect.Timeout)

【解决方案3】：

time.Duration 的解组在 yaml.v3、https://play.golang.org/p/-6y0zq96gVz 中工作

package main

import (
    "fmt"
    "time"
    
    "gopkg.in/yaml.v3"
)

type Config struct {
    Timeout time.Duration `yaml:"timeout"`
}

func main() {
    var cfg Config

    b := []byte(`timeout: 60s`)
    yaml.Unmarshal(b, &cfg)
    fmt.Printf("timeout: %dm", int(cfg.Timeout.Minutes()))
}

【讨论】：

【解决方案4】：

目前它也适用于gopkg.in/yaml.v2，因此接受的答案已过时

https://play.golang.org/p/lbragq1QNqD

package main

import (
    "fmt"
    "time"

    "gopkg.in/yaml.v2"

)

type Config struct {
    Timeout time.Duration `yaml:"timeout"`
}


func main() {
    sample := `
timeout: 1s
`
    var b Config
    if err := yaml.Unmarshal([]byte(sample), &b); err != nil {
        panic(err)
    }
    fmt.Printf("%+v", b)
}

【讨论】：

【解决方案5】：

type system struct {
    ...
    TokenLifeTime yamlTimeDur  `yaml:"TokenLifeTime"`
}

type yamlTimeDur time.Duration

func (t *yamlTimeDur) UnmarshalYAML(unmarshal func(interface{}) error) error {
    var tm string
    if err := unmarshal(&tm); err != nil {
        return err
    }

    td, err := time.ParseDuration(tm)
    if err != nil {
        return fmt.Errorf("failed to parse '%s' to time.Duration: %v", tm, err)
    }

    *t = yamlTimeDur(td)
    return nil
}

func (t *yamlTimeDur) Duration() time.Duration {
    return time.Duration(*t)
}

【讨论】：