英文:
Golang problems with referencing arrays of sub structures
问题
我遇到了一个问题，不知道如何引用子结构的元素。
参考：http://play.golang.org/p/pamS_ZY01s
给定以下代码...如何引用room结构中的数据？我尝试了fmt.Println(*n.Homes[0].Rooms[0].Size)，但是不起作用。
代码示例如下：
package main
import (
"fmt"
)
type Neighborhood struct {
Name string
Homes *[]Home
}
type Home struct {
Color string
Rooms *[]Room
}
type Room struct {
Size string
}
func main() {
var n Neighborhood
var h1 Home
var r1 Room
n.Name = "Mountain Village"
h1.Color = "Blue"
r1.Size = "200 sq feet"
// 初始化Homes数组
homeslice := make([]Home, 0)
n.Homes = &homeslice
roomslice := make([]Room, 0)
h1.Rooms = &roomslice
*h1.Rooms = append(*h1.Rooms, r1)
*n.Homes = append(*n.Homes, h1)
fmt.Println(n)
fmt.Println(*n.Homes)
}
英文:
I am having a problem figuring out how to reference elements of a sub structure.
See: http://play.golang.org/p/pamS_ZY01s
Given something like following.... How do you reference data in the room struct? I have tried fmt.Println(*n.Homes[0].Rooms[0].Size), but that does not work.
Begin Code example
package main
import (
"fmt"
)
type Neighborhood struct {
Name string
Homes *[]Home
}
type Home struct {
Color string
Rooms *[]Room
}
type Room struct {
Size string
}
func main() {
var n Neighborhood
var h1 Home
var r1 Room
n.Name = "Mountain Village"
h1.Color = "Blue"
r1.Size = "200 sq feet"
// Initiaize Array of Homes
homeslice := make([]Home, 0)
n.Homes = &homeslice
roomslice := make([]Room, 0)
h1.Rooms = &roomslice
*h1.Rooms = append(*h1.Rooms, r1)
*n.Homes = append(*n.Homes, h1)
fmt.Println(n)
fmt.Println(*n.Homes)
}
答案1
得分: 4
首先，*[]Home 是非常浪费的。在底层，切片是一个由三个字组成的结构体，其中一个是指向数组的指针。你在这里引入了双重间接引用。这篇关于Go语言数据结构的文章非常有用。
现在，由于这种间接引用，你需要在每个指向切片的指针表达式中加上解引用运算符 *。像这样：
fmt.Println((*(*n.Homes)[0].Rooms)[0].Size)
但是，实际上，只需去掉指针即可。
英文:
First, *[]Home is really wasteful. A slice is a three worded struct under the hood, one of them being itself a pointer to an array. You are introducing a double indirection there. This article on data structures in Go is very useful.
Now, because of this indirection, you need to put the dereference operator * in every pointer-to-slice expression. Like this:
fmt.Println((*(*n.Homes)[0].Rooms)[0].Size)
But, really, just take out the pointers.
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