dongshuo6185
2017-01-04 09:49
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如何将utf8字符串转换为[] byte?

I want to unmarshal a string that contains JSON, however the Unmarshal function takes a []byte as input.

How can I convert my UTF8 string to []byte?

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我想解组包含JSON的 string ,\无论如何, Unmarshal 函数需要一个 [] byte 作为输入。

如何将我的UTF8 string 转换为 [ ] byte

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  • douerqu2319 2017-01-04 10:00
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    This question is a possible duplicate of How to assign string to bytes array, but still answering it as there is a better, alternative solution:

    Converting from string to []byte is allowed by the spec, using a simple conversion:

    Conversions to and from a string type

    [...]

    1. Converting a value of a string type to a slice of bytes type yields a slice whose successive elements are the bytes of the string.

    So you can simply do:

    s := "some text"
    b := []byte(s) // b is of type []byte
    

    However, the string => []byte conversion makes a copy of the string content (it has to, as strings are immutable while []byte values are not), and in case of large strings it's not efficient. Instead, you can create an io.Reader using strings.NewReader() which will read from the passed string without making a copy of it. And you can pass this io.Reader to json.NewDecoder() and unmarshal using the Decoder.Decode() method:

    s := `{"somekey":"somevalue"}`
    
    var result interface{}
    err := json.NewDecoder(strings.NewReader(s)).Decode(&result)
    fmt.Println(result, err)
    

    Output (try it on the Go Playground):

    map[somekey:somevalue] <nil>
    

    Note: calling strings.NewReader() and json.NewDecoder() does have some overhead, so if you're working with small JSON texts, you can safely convert it to []byte and use json.Unmarshal(), it won't be slower:

    s := `{"somekey":"somevalue"}`
    
    var result interface{}
    err := json.Unmarshal([]byte(s), &result)
    fmt.Println(result, err)
    

    Output is the same. Try this on the Go Playground.

    Note: if you're getting your JSON input string by reading some io.Reader (e.g. a file or a network connection), you can directly pass that io.Reader to json.NewDecoder(), without having to read the content from it first.

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  • dqwyghl0649 2017-01-04 09:56

    just use []byte(s) on the string. for example:

    package main
    
    import (
        "encoding/json"
        "fmt"
    )
    
    func main() {
        s := `{"test":"ok"}`
        var data map[string]interface{}
        if err := json.Unmarshal([]byte(s), &data); err != nil {
            panic(err)
        }
        fmt.Printf("json data: %v", data)
    }
    

    check it out on the playground here.

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