Курнат Андрей
62 lines
1.5 KiB
Go
62 lines
1.5 KiB
Go
package reflects
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import (
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"fmt"
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"reflect"
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)
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// MakeSliceByElem create a new slice by the element type.
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//
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// - elType: the type of the element.
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// - returns: the new slice.
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//
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// Usage:
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//
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// sl := MakeSliceByElem(reflect.TypeOf(1), 10, 20)
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// sl.Index(0).SetInt(10)
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//
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// // Or use reflect.AppendSlice() merge two slice
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// // Or use `for` with `reflect.Append()` add elements
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func MakeSliceByElem(elTyp reflect.Type, len, cap int) reflect.Value {
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return reflect.MakeSlice(reflect.SliceOf(elTyp), len, cap)
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}
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// FlatSlice flatten multi-level slice to given depth-level slice.
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//
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// Example:
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//
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// FlatSlice([]any{ []any{3, 4}, []any{5, 6} }, 1) // Output: []any{3, 4, 5, 6}
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//
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// always return reflect.Value of []any. note: maybe flatSl.Cap != flatSl.Len
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func FlatSlice(sl reflect.Value, depth int) reflect.Value {
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items := make([]reflect.Value, 0, sl.Cap())
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slCap := addSliceItem(sl, depth, func(item reflect.Value) {
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items = append(items, item)
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})
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flatSl := reflect.MakeSlice(reflect.SliceOf(anyType), 0, slCap)
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flatSl = reflect.Append(flatSl, items...)
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return flatSl
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}
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func addSliceItem(sl reflect.Value, depth int, collector func(item reflect.Value)) (c int) {
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for i := 0; i < sl.Len(); i++ {
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v := Elem(sl.Index(i))
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if depth > 0 {
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if v.Kind() != reflect.Slice {
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panic(fmt.Sprintf("depth: %d, the value of index %d is not slice", depth, i))
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}
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c += addSliceItem(v, depth-1, collector)
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} else {
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collector(v)
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}
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}
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if depth == 0 {
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c = sl.Cap()
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}
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return c
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}
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