在Go中，如何使用切片创建通用函数？

Question

Let's say I want to write a function that finds a value in a slice

I intuitively want to write:

func find(s []interface{}, f func(interface{})bool) int {
    for i, item := range s {
        if f(item) {
            return i
        }
    }
    return -1
}

however I don't manage to do this with Go. I could have an interface with

Len() int
Value(int) interface{}
...

and this would work but in my real code things are more complicated (I need to do slices[from:end] etc), append, ... etc and if I redefine all this in an interface I end up having a lot of code. Is there a better way?

Answer 1

You can use reflection. I wrote this function for a project, feel free to use it:

// InSlice returns true if value is in slice
func InSlice(value, slice interface{}) bool {
    switch reflect.TypeOf(slice).Kind() {
    case reflect.Slice, reflect.Ptr:
        values := reflect.Indirect(reflect.ValueOf(slice))
        if values.Len() == 0 {
            return false
        }

        val := reflect.Indirect(reflect.ValueOf(value))

        if val.Kind() != values.Index(0).Kind() {
            return false
        }

        for i := 0; i < values.Len(); i++ {
            if reflect.DeepEqual(values.Index(i).Interface(), val.Interface()) {
                return true
            }
        }
    }
    return false
}