英文:
Generics with nested maps
问题
目前我正在使用类似这样的代码：
package hellotype object map[string]interface{}func (o object) get(key string) object {val, _ := o[key].(object)return val}func (o object) getInt(key string) int {val, _ := o[key].(int)return val}
但问题是，我必须为每种要返回的类型编写一个函数。我尝试使用类似这样的代码：
package hellotype object map[string]interface{}// 语法错误：方法不能有类型参数func (o object) get[T object|int](key string) T {val, _ := o[key].(T)return val}
然后我尝试了这样的代码：
package hellotype object map[string]interface{}type token[T object|int] struct {in objectout T}func (t token[T]) get(key string) token[T] {t.out, _ = t.in[key].(T)return t}
这段代码可以编译通过，但由于in从未更新，我认为我无法进行链式调用，例如对于嵌套的映射：
something.get("one").get("two").get("three")
是否有可能使用泛型来实现与我的原始代码类似的结果，但不需要复制粘贴函数？
英文:
Currently I am using some code like this:
package hellotype object map[string]interface{}func (o object) get(key string) object {val, _ := o[key].(object)return val}func (o object) getInt(key string) int {val, _ := o[key].(int)return val}
but the issue is, I have to write a function for every type I want to return. I
tried using something like this:
package hellotype object map[string]interface{}// syntax error: method must have no type parametersfunc (o object) get[T object|int](key string) T {val, _ := o[key].(T)return val}
then I did this:
package hellotype object map[string]interface{}type token[T object|int] struct {in objectout T}func (t token[T]) get(key string) token[T] {t.out, _ = t.in[key].(T)return t}
which compiles, but since in never gets updated, I don't think I could do chaining, for a nested map:
something.get("one").get("two").get("three")
Is it possible to do something with generics, to give a similar result to my original code, but without having the copy paste functions?
答案1
得分: 1
我想我弄明白了。你可以创建一个包装类型，它包含当前对象以及输出值。如果有其他想法，我也很感兴趣：
package maintype object map[string]interface{}type token[T any] struct {objectvalue T}func newToken[T any](m object) token[T] {return token[T]{object: m}}func (t token[T]) get(key string) token[T] {switch val := t.object[key].(type) {case object:t.object = valcase T:t.value = val}return t}
示例：
package mainfunc main() {obj := object{"one": object{"two": object{"three": 3},},}three := newToken[int](obj).get("one").get("two").get("three")println(three.value == 3)}
英文:
I think I figured it out. You can create a wrapper type, that holds the current
object, as well as the output value. If anyone has other ideas, I am interested
in them as well:
package maintype object map[string]interface{}type token[T any] struct {objectvalue T}func newToken[T any](m object) token[T] {return token[T]{object: m}}func (t token[T]) get(key string) token[T] {switch val := t.object[key].(type) {case object:t.object = valcase T:t.value = val}return t}
Example:
package mainfunc main() {obj := object{"one": object{"two": object{"three": 3},},}three := newToken[int](obj).get("one").get("two").get("three")println(three.value == 3)}
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