英文:
Create an interface that is a slice of another interface
问题
我想做类似以下的事情：
type Model interface {
EntityType() string
GetKey() *datastore.Key
SetKey(*datastore.Key) error
PreSave(context.Context) error
PostSave(context.Context) error
PostLoad(context.Context) error
}
type Models []Model
func (m Models) Prepare(num int) ([]Model, error) {
// 进行 Models 切片的准备工作
}
这样，Models 结构体也是一个接口，并且会由实现 Model 接口的结构体切片来实现。类似以下的代码：
type Foo struct {
key *datastore.Key `datastore:"_"`
// ... 其他字段
}
// 假设所有 Model 接口的函数都在这里并且有效
type Foos []Foo
func (f Foos) Prepare(num int) ([]Model, error) {
// 进行 Foo 切片的准备工作
}
显然，上面的代码会抛出错误并且不可行。但是是否有一些代码可以产生基本相同的功能？而不使用 reflect 或其他昂贵的操作呢？
英文:
I'd like to do something like the following:
type Model interface {
EntityType() string
GetKey() *datastore.Key
SetKey(*datastore.Key) error
PreSave(context.Context) error
PostSave(context.Context) error
PostLoad(context.Context) error
}
type Models []Model interface {
Prepare(int) ([]Model, error)
}
So that the struct Models is also an interface and would get implemented by a slice of the structs that implement Model. Something like the following:
type Foo struct {
key *datastore.Key `datastore:"_"`
// ... other things here
}
// assume all Model interface funcs are here and valid
type Foos []Foo
func (f *Foos) Prepare (num int) ([]Model, error) {
// do the preparations for Foo slice
}
Obviously, the code above throws errors and isn't possible. But is there some code that would produce basically the same functionality? Without using reflect or anything costly like that?
答案1
得分: 1
显然，一个简单的代码片段如下：
type Models interface {
Prepare(int) ([]Model, error)
}
type Foos []Foo
func (f Foos) Prepare(num int) ([]Model, error) {
// 对 Foo 切片进行准备工作
return nil, nil
}
func main() {
foos := Foos{}
models := Models(foos)
models.Prepare(17)
}
那么你的实际问题是什么？请参考 https://golang.org/doc/faq#covariant_types 和 https://golang.org/doc/faq#convert_slice_of_interface，这些链接可能会更清楚一些。
我建议提供操作 []Model 的函数（而不是方法），而不是将模型切片抽象为某个更高级的类型。
英文:
Obviously a simple
type Models interface {
Prepare(int) ([]Model, error)
}
type Foos []Foo
func (f Foos) Prepare(num int) ([]Model, error) {
// do the preparations for Foo slice
return nil, nil
}
func main() {
foos := Foos{}
models := Models(foos)
models.Prepare(17)
}
works.
So what is your actual question? Please see also https://golang.org/doc/faq#covariant_types and https://golang.org/doc/faq#convert_slice_of_interface
Which should make it a bit clearer.
I would recommend to provide function (! not methods) to operate on []Model and not to abstract the slice-of-model into some higher type.
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