Reflection Go中的泛型编程。避免硬编码类型断言
我正在编写一个通用缓存机制,我需要在结构中设置一些属性,只知道它们的reflect.Type、属性名称和reflect.Value要在属性中设置,但我无法避免类型断言,这使得我的代码不是通用的Reflection Go中的泛型编程。避免硬编码类型断言,reflection,go,generic-programming,Reflection,Go,Generic Programming,我正在编写一个通用缓存机制,我需要在结构中设置一些属性,只知道它们的reflect.Type、属性名称和reflect.Value要在属性中设置,但我无法避免类型断言,这使得我的代码不是通用的 func main() { addressNew := Address{"New Address description!"} // In the real problem, i know the reflect.Type of value, but // the struct
func main() {
addressNew := Address{"New Address description!"}
// In the real problem, i know the reflect.Type of value, but
// the struct came to me as a interface{}, just like this method
// Return many kinds of values from redis as interface{},
// (Customer, Order, Address, Product, SKU etc), in a generic way,
// but returns the reflect.Type of value also.
interfaceSomeValue := getMyValue()
fmt.Printf("%v", interfaceSomeValue)
fmt.Println("")
// This portion of code comes from my cache mechanism, that is a library
// used by other projects. My cache lib really can't know all others
// type structs to perform the type assertion, but the cache mechanism know
// the reflect.Type of the interface.
// If you try at this way, will cause a panic by try to access a FieldByName
// in a interface, because the Customer comes from getMyValue and
// becomes a interface{}, and now a type assertion is
// required -> http://play.golang.org/p/YA8U9_KzC9
newCustomerNewAttribute := SetAttribute(&interfaceSomeValue, "Local", interface{}(addressNew), reflect.TypeOf(Customer{}))
fmt.Printf("%v", newCustomerNewAttribute)
fmt.Println("")
}
func SetAttribute(object interface{}, attributeName string, attValue interface{}, objectType reflect.Type) interface{} {
if reflect.ValueOf(object).Kind() != reflect.Ptr {
panic("need a pointer")
}
value := reflect.ValueOf(object).Elem()
field := value.FieldByName(attributeName)
valueForAtt := reflect.ValueOf(attValue)
field.Set(valueForAtt)
return value.Interface()
}
我终于找到了一种方法。请按照下面的“围棋场”和代码片段进行操作:
你能提供一个小的例子来说明你要解决的问题吗?类型断言对于尝试泛型编程的go程序来说是正常的。谢谢你的回答,Karmastan。实际上我在围棋场上举了个例子。我从缓存存储(Redis)中获取要放入属性中的值,但是从存储中获取该值的函数返回一个接口和关于该值的reflect.Type。请注意,我的系统中可能有数百种类型的结构,这破坏了我的通用代码。。。谢谢你的帮助。请准确地展示你正在努力实现的目标。这与你的上一个问题相同,但还有一层间接的意思。您没有解释为什么需要类型断言,以及为什么不能只使用反射。
//new approach SetAttribute, without any hard coded type assertion, just based on objectType parameter
func SetAttribute(myUnknownTypeValue *interface{}, attributeName string, attValue interface{}, objectType reflect.Type) {
// create value for old val
oldValue := reflect.ValueOf(*myUnknownTypeValue)
//create a new value, based on type
newValue := reflect.New(objectType).Elem()
// set the old value to the new one, making the
// implicit type assertion, not hard coding that.
newValue.Set(oldValue)
//set value attribute to the new struct, copy of the old one
field := newValue.FieldByName(attributeName)
valueForAtt := reflect.ValueOf(attValue)
field.Set(valueForAtt)
//capture the new value from reflect.Value
newValInterface := newValue.Interface()
//set the new value to the pointer
*myUnknownTypeValue = newValInterface
}