如何优雅地将一个数组的一部分复制到另一个数组中或注入到另一个数组中

Question

I have the following code which works but the point here is that I want to inject or insert one array of arbitrary length into another statically sized array extending its length:

package main

import (
    "fmt"
)

func main() {
    ffmpegArguments := []string{
        "-y",
        "-i", "invideo",
        // ffmpegAudioArguments...,
        "-c:v", "copy",
        "-strict", "experimental",
        "outvideo",
    }

    var outputArguments [12]string
    copy(outputArguments[0:3], ffmpegArguments[0:3])
    copy(outputArguments[3:7], []string{"-i", "inaudio", "-c:a", "aac"})
    copy(outputArguments[7:12], ffmpegArguments[3:8])

    fmt.Printf("%#v
", ffmpegArguments)
    fmt.Printf("%#v
", outputArguments)
}

https://play.golang.org/p/peQXkOpheK4

Answer 1

I ended up modifying the answer from @Alirus by making a copy of the array first because it appears that the first assignment points to the haystack array and subsequent steps modify the haystack slice:

// arrayInject is a helper function written by Alirus on StackOverflow in my
// inquiry to find a way to inject one array into another _elegantly_:
// https://stackoverflow.com/a/53647212/776896
func arrayInject(haystack, pile []string, at int) (result []string) {
    result = make([]string, len(haystack[:at]))
    copy(result, haystack[:at])
    result = append(result, pile...)
    result = append(result, haystack[at:]...)

    return result
}

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