main.go 源码
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials : https://learngoprogramming.com
// In-person training : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus
package main
import (
"fmt"
"github.com/inancgumus/learngo/16-slices/exercises/23-limit-the-backing-array-sharing/api"
)
// ---------------------------------------------------------
// EXERCISE: Limit the backing array sharing
//
// GOAL
//
// Limit the capacity of the slice that is returned
// from the `Read` function. Read on for more details.
//
//
// BEFORE YOU START
//
// In this exercise: API means the api package. It's in the
// api folder. You need to change the code in the `api/api.go`
// to solve this exercise, and you need import the api
// package.
//
//
// WHAT IS THE PROBLEM?
//
// `Read` function of the api package returns a portion of
// its `temps` slice. Below, `main()` saves it to the
// `received` slice.
//
// `main()` appends to the `received` slice but doing so
// also changes the backing array of the `temps` slice.
// We don't want that.
//
// `main()` can change the part of the `temps` slice
// that is returned from the `Read()`, but it shouldn't
// be able to change the elements in the rest of the
// `temps`.
//
//
// WHAT YOU NEED TO DO?
//
// So you need to limit the capacity of the returned
// slice somehow. Remember: `received` and `temps`
// share the same backing array. So, appending to it
// can overwrite the same backing array.
//
//
// CURRENT
//
// | |
// v v
// api.temps : [5 10 3 1 3 80 90]
// main.received : [5 10 3 1 3]
// ^ ^ append changes the `temps`
// slice's backing array.
//
//
//
// EXPECTED
//
// The corrected api package does not allow the `main()` to
// change unreturned portion of the temps slice's backing array.
// | |
// v v
// api.temps : [5 10 3 25 45 80 90]
// main.received : [5 10 3 1 3]
//
// ---------------------------------------------------------
func main() {
// DO NOT CHANGE ANYTHING IN THIS CODE.
// get the first three elements from api.temps
received := api.Read(0, 3)
// append changes the api package's temps slice's
// backing array as well.
received = append(received, []int{1, 3}...)
fmt.Println("api.temps :", api.All())
fmt.Println("main.received :", received)
}
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