如何在没有构造函数的情况下在 Go 中正确初始化切片内的结构

Question

Go 没有构造函数，所以我想知道如何正确初始化切片内的结构。我很难相信答案是初始化并复制所有结构两次？

package main

import "fmt"

// minQueueLen is smallest capacity that queue may have.
// Must be power of 2 for bitwise modulus: x % n == x & (n - 1).
const minQueueLen = 16

type Queue[T any] struct {
    buf []T
}

func New[T any]() *Queue[T] {
    return &Queue[T]{
        buf: make([]T, minQueueLen),
    }
}

type SomeStruct struct {
    q Queue[int]
}

func main() {
    someSlice := make([]SomeStruct, 10)

    // Now buf is the wrong size because we didn't
    // get to init it with the proper constructor.
    // It would be very wasteful to initialize this
    // struct twice (100s of thousands or more).

    fmt.Println("Size of a buf: ", len(someSlice[0].q.buf))
}

下面是一个示例，其中队列的缓冲区必须是 2 的幂。

Answer 1

你从未真正初始化过它。分配切片只是分配空间，但不会初始化各个元素。获得切片后，您可以循环遍历它并初始化：

func main() {
    someSlice := make([]SomeStruct, 10)

    for i:=range someSlice {
       someSlice[i].q=*New[int]()
    }

    fmt.Println("Size of a buf: ", len(someSlice[0].q.buf))
}

您还可以执行以下操作：

func (s *SomeStruct) Init()  {
    s.q=Queue[int]{
        buf: make([]int, minQueueLen),
    }
}


func main() {
    someSlice := make([]SomeStruct, 10)

    for i:=range someSlice {
       someSlice[i].Init()
    }

    fmt.Println("Size of a buf: ", len(someSlice[0].q.buf))
}