英文:
How to properly init structs in Go inside slices without constructors
问题
Go语言没有构造函数，所以我想知道如何在切片中正确初始化结构体。我很难相信答案会是初始化并复制所有结构体两次。
这是一个示例，其中队列的缓冲区必须是2的幂。
package mainimport "fmt"// minQueueLen is smallest capacity that queue may have.// Must be power of 2 for bitwise modulus: x % n == x & (n - 1).const minQueueLen = 16type 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)// 现在buf的大小是错误的，因为我们没有使用正确的构造函数进行初始化。// 初始化这个结构体两次（成千上万次）将非常浪费资源。fmt.Println("Size of a buf: ", len(someSlice[0].q.buf))}
以上是一个示例，其中队列的缓冲区必须是2的幂。
英文:
Go doesn't have constructors so I'm wondering how you would properly initialize a struct inside a slice. I have trouble believing that the answer would be to initialize and copy all the structs twice?
package mainimport "fmt"// minQueueLen is smallest capacity that queue may have.// Must be power of 2 for bitwise modulus: x % n == x & (n - 1).const minQueueLen = 16type 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))}
Here is an example where the buffer of the queue must be a power of 2.
答案1
得分: 0
你从未真正初始化它。分配一个切片只是分配了空间，但并没有初始化各个元素。一旦你有了切片，你可以遍历它并进行初始化：
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))}
你也可以这样做：
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))}
英文:
You never really initialized it. Allocating a slice simply allocates the space, but does not initialize individual elements. Once you have the slice, you can loop through it and inialize:
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))}
You can also do:
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))}
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