Function get

builtin/lib.go:546–618

(params ...any)

}

func get(params ...any) (out any, err error) {
	if len(params) < 2 {
		return nil, fmt.Errorf("invalid number of arguments (expected 2, got %d)", len(params))
	}
	from := params[0]
	i := params[1]
	v := reflect.ValueOf(from)

	if from == nil {
		return nil, nil
	}

	if v.Kind() == reflect.Invalid {
		panic(fmt.Sprintf("cannot fetch %v from %T", i, from))
	}

	// Methods can be defined on any type.
	if v.NumMethod() > 0 {
		if methodName, ok := i.(string); ok {
			method := v.MethodByName(methodName)
			if method.IsValid() {
				return method.Interface(), nil
			}
		}
	}

	switch v.Kind() {
	case reflect.Array, reflect.Slice, reflect.String:
		index := runtime.ToInt(i)
		l := v.Len()
		if index < 0 {
			index = l + index
		}
		if 0 <= index && index < l {
			value := v.Index(index)
			if value.IsValid() {
				return value.Interface(), nil
			}
		}

	case reflect.Map:
		var value reflect.Value
		if i == nil {
			value = v.MapIndex(reflect.Zero(v.Type().Key()))
		} else {
			value = v.MapIndex(reflect.ValueOf(i))
		}
		if value.IsValid() {
			return value.Interface(), nil
		}

	case reflect.Struct:
		fieldName := i.(string)
		value := v.FieldByNameFunc(func(name string) bool {
			field, _ := v.Type().FieldByName(name)
			switch field.Tag.Get("expr") {
			case "-":
				return false