一片类型结构访问索引超出范围

Question

I am trying to use slice of type struct. Look at the following sample

package main

import (
    "fmt"
)

func main() {

    arr := []struct {
        A string
        B string
    } {}

    arr[0].A = "I am"
    arr[0].B = "First"

    arr[1].A = "I am"
    arr[1].B = "Second"

    fmt.Println(arr)

}

When I compile this code I've got out of range error. Why?

Answer 1

You need to append new elements to your slice (if you don't make an array as in FUZxxl's answer.
It is easier with a named type instead of a type literal.

See "Appending to and copying slices" and "Arrays, slices (and strings): The mechanics of 'append'".

Example <kbd>play.golang.org</kbd>

package main

import (
    "fmt"
)

func main() {

    type T struct {
        A string
        B string
    }

    arr := []T{}

    arr = append(arr, T{A: "I am", B: "First"})
    arr = append(arr, T{A: "I am", B: "Second"})

    fmt.Println(arr)
}

Output:

[{I am First} {I am Second}]