英文:
How to test if a generic type can fit a more restrictive interface - golang
问题
我正在构建一个通用的数据结构，我打算在不同的上下文和使用不同的数据位使用它。
我目前正在尝试创建一个匹配器，它将查找我的数据结构并返回包含给定数据的所有节点。我的问题是，由于我希望我的数据结构尽可能通用，我需要我的数据是与any匹配的通用类型，这将不允许我进行相等性比较。
我已经构建了一个“后代类型”（可能有一个正确的术语，我是自学的），它具有更严格的comparable约束。
我想知道是否可以从更通用的类型转换为更具体的类型（即使我必须捕获错误并将其返回给用户）。我知道我不是特别需要这样做，但如果我这样做，代码在后续阶段会更容易理解。
这里有一段代码来解释我的问题：
type DataStructureGeneralCase[T any] struct {
/*
我的数据结构，太长了，不适合作为一个好的示例，所以我使用了一个切片
*/
data []T
}
type DataStructureSpecific[T comparable] DataStructureGeneralCase[T]
// 这个可以工作，因为any包含comparable
func (ds *DataStructureSpecific[T]) GetMatching(content T) int {
/*实际函数返回我的自定义节点类型，但让我们简短一些*/
for idx, item := range ds.data {
if item == content {
return idx
}
}
return -1
}
func (dg *DataStructureGeneralCase[T]) TryMatching(content T) (int, error) {
if ds, ok := (*dg).(DataStructureGeneralCase); ok {
// 这不起作用，因为dg不是接口，我理解
} else {
return -1, fmt.Errorf("由于非可比较的内容，无法进行转换")
}
}
我的问题可以总结为“我该如何进行转换？”
英文:
I am building an all-purpose data structure, that I intend to use in various contexts and with various bits of data.
I am currently attempting to make a matcher, that will look into my structure and return all nodes containing the data given. My problem being that, since I need my structure to be as generic as possible, I need my data to be of a generic type matching any, and this won't allow me to make equalities.
I have built a "descendant type" (there's probably a correct term, I'm self-taught on this) that has the more rigorous comparable constraint.
I want to see if I can convert from the more general one to the more specific one (even if I have to catch an error and return it to the user). I know that I don't specifically need to, but it makes the code understandable down the line if i do it like that.
Here's a bit of code to explain my question :
type DataStructureGeneralCase[T any] struct {
/*
my data structure, which is too long to make for a good example, so I'm using a slice instead
*/
data []T
}
type DataStructureSpecific[T comparable] DataStructureGeneralCase[T]
// this works because any contains comparable
func (ds *DataStructureSpecific[T]) GetMatching(content T) int {
/*The real function returns my custom Node type, but let's be brief*/
for idx, item := range ds.data {
if item == content {
return idx
}
}
return -1
}
func (dg *DataStructureGeneralCase[T]) TryMatching(content T) (int, error) {
if ds, ok := (*dg).(DataStructureGeneral); ok {
// Does not work because dg is not interface, which I understand
} else {
return -1, fmt.Errorf("Could not convert because of non-comparable content")
}
}
My question can be summarized to "How can I do my conversion ?".
答案1
得分: 3
func CheckImplements[T any, I any]() bool {
var o T
_, ok := interface{}(&o).(I)
return ok
}
所以，只是运行时。
英文:
func CheckImplements[T any, I any]() bool {
var o T
_, ok := interface{}(&o).(I)
return ok
}
So yeah, runtime only.
答案2
得分: 0
首先将其转换为空接口：
castedDg := interface{}(dg)
if ds, ok := castedDg.(DataStructureGeneralCase[T]); ok {
他们在https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#why-not-permit-type-assertions-on-values-whose-type-is-a-type-parameter中解释了为什么选择这种方法。
英文:
Cast to the empty interface first:
castedDg := interface{}(dg)
if ds, ok := castedDg.(DataStructureGeneralCase[T]); ok {
They explain why they chose this approach in https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md#why-not-permit-type-assertions-on-values-whose-type-is-a-type-parameter
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