获取可为空字符串的长度

Question

I have the following structure:

type NetAuth struct {
        Identificator *string `json:"identificator"`
        Password      *string `json:"password"`
        DeviceID      *string `json:"deviceId"`
        Type          int  `json:"type"`
}

I am trying to get the length of Identificator with len(event.Identificator) however I get Invalid argument for len

Before calling len I check if it's nil. I am coming from Java/C#/PHP background and it's my first time writing in GO.

Answer 1

There is no simple len(string) concept in Go. You either need the number of bytes in the string representation or the number of characters (so called runes). For ASCII strings both values are the same while for unicode-encoded strings they are usually different.

import "unicode/utf8"

// Firt check that the pointer to your string is not nil
if nil != event.Identificator {
    // For number of runes:
    utf8.RuneCountInString(*event.Identificator)

    // For number of bytes:
    len(*event.Identificator)
}

For more information you can check this answer https://stackoverflow.com/a/12668840/1201488.

UPD: event.Identificator is a pointer to a string value in the NetAuth structure rather than a string value. So you need to dereference it first via *event.Identificator.