英文:
How do you have a struct with a pointer to an array in it in Go?
问题
我本来以为这段代码会工作的：
package main
type Item struct {
Key string
Value string
}
type Blah struct {
Values []Item
}
func main() {
var list = [...]Item {
Item {
Key : "Hello1",
Value : "World1",
},
Item {
Key : "Hello1",
Value : "World1",
},
}
_ = Blah {
Values : &list,
}
}
我以为这是正确的做法；Values是一个切片，list是一个数组。&list应该是一个切片，可以赋值给Item[]，对吗？
...但是实际上，它报错了，错误信息是：
cannot use &list (type *[2]Item) as type []Item in assignment
在C语言中，你会这样写：
struct Item {
char *key;
char *value;
};
struct Blah {
struct Item *values;
};
在Go语言中该怎么做呢？
我看到了这个问题：
https://stackoverflow.com/questions/2439453/go-using-a-pointer-to-array
...但是要么答案是针对Go的旧版本，要么就是完全错误的。:/
英文:
I would have expected this code to work:
package main
type Item struct {
Key string
Value string
}
type Blah struct {
Values []Item
}
func main() {
var list = [...]Item {
Item {
Key : "Hello1",
Value : "World1",
},
Item {
Key : "Hello1",
Value : "World1",
},
}
_ = Blah {
Values : &list,
}
}
I thought this would be the correct way of doing this; Values is a slice, list is an array. &list should be a slice, which is assignable to Item[], right?
...but instead, it errors with the message:
cannot use &list (type *[2]Item) as type []Item in assignment
In C, you'd write:
struct Item {
char *key;
char *value;
};
struct Blah {
struct Item *values;
};
How do you do that in Go?
I saw this question:
https://stackoverflow.com/questions/2439453/go-using-a-pointer-to-array
...but either the answers are for a previous version of Go, or they're just plain wrong. :/
答案1
得分: 4
一个切片不仅仅是一个指向数组的指针，它还有一个内部表示，其中包含它的长度和容量。
如果你想从list中获取一个切片，你可以这样做：
_ = Blah {
Values : list[:],
}
英文:
A slice is not simply a pointer to an array, it has an internal representation which contains its length and capacity.
If you want to get a slice from list you can do:
_ = Blah {
Values : list[:],
}
答案2
得分: 3
Go是一种幸运的语言，它并不像OP所看起来的那样冗长。这段代码可以工作：
package main
type Item struct {
Key, Value string
}
type Blah struct {
Values []Item
}
func main() {
list := []Item{
{"Hello1", "World1"},
{"Hello2", "World2"},
}
_ = Blah{list[:]}
}
（也可以在这里找到）
PS：我建议不要在Go中编写C代码。
英文:
Go is, fortunately, not so verbose as it might seem from the OP. This works:
package main
type Item struct {
Key, Value string
}
type Blah struct {
Values []Item
}
func main() {
list := []Item{
{"Hello1", "World1"},
{"Hello2", "World2"},
}
_ = Blah{list[:]}
}
(Also here)
PS: Let me suggest to not write C in Go.
答案3
得分: 2
当你开始使用Go时，我建议完全忽略数组，只使用切片。数组很少使用，并且会给Go初学者带来很多麻烦。如果你有一个切片，你就不需要一个指向它的指针，因为它是一个引用类型。
这是你的示例，使用切片而没有指针，更符合惯用方式。
package main
type Item struct {
Key string
Value string
}
type Blah struct {
Values []Item
}
func main() {
var list = []Item{
Item{
Key: "Hello1",
Value: "World1",
},
Item{
Key: "Hello1",
Value: "World1",
},
}
_ = Blah{
Values: list,
}
}
英文:
When you are starting out with Go ignore arrays completely and just use slices is my advice. Arrays are rarely used and cause Go beginners a lot of trouble. If you have a slice then you don't need a pointer to it since it is a reference type.
Here is your example with a slice and no pointers which is much more idiomatic.
package main
type Item struct {
Key string
Value string
}
type Blah struct {
Values []Item
}
func main() {
var list = []Item{
Item{
Key: "Hello1",
Value: "World1",
},
Item{
Key: "Hello1",
Value: "World1",
},
}
_ = Blah{
Values: list,
}
}
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