英文:
go: type assert of interface
问题
我有一个关于创建结构体动态模型的问题。我的意思是，根据传入的数据结构，我想要断言、转换或者仅仅改变结构体的类型。
如果sourceName变量是type_x，那么deserializedData的类型应该是type_x；如果是type_y，那么就是type_y。如何动态地设置变量deserializedData？
我代码中的这部分如下：
....
var cacheData []byte
var deserializedData models.NoaggModel
cache_err := cache.Get(string(string(sourceName) + "_" + string(t.Date)), &cacheData)
if cache_err != nil {
fmt.Println("cache_error: ", cache_err)
panic("the cache is empty")
}
err2 := json.Unmarshal([]byte(cacheData), &deserializedData)
if err2 == nil {
fmt.Println("deserialized data: " + string(sourceName), deserializedData)
}
for _, chart := range charts {
w.Name = chart.Name
if err2 == nil {
w.Data = countDataByName(sourceName, deserializedData, t.Request.Filters, string(chart.Name))
}
out <- w
}
....
如何修改它，以避免严格设置models.NoaggModel类型？
英文:
I have a problem with making dynamic model of a struct. I mean that I want to assert or cast, or just change the type of struct according to the incoming data strut.
if sourceName variable would be type_x , than the type of deserializedData should be type_x, if type_y, than type_y. How to set the variable deserializedData dynamicly for this ?
I have this part in my code:
....
var cacheData []byte
var deserializedData models.NoaggModel
cache_err := cache.Get(string(string(sourceName) + "_" + string(t.Date)), &cacheData);
if cache_err != nil {
fmt.Println("cache_error: ", cache_err)
panic("the cache is empty")
}
err2 := json.Unmarshal([]byte(cacheData), &deserializedData)
if err2 == nil {
fmt.Println("deserialized data: " + string(sourceName), deserializedData)
}
for _, chart := range charts {
w.Name = chart.Name
if err2 == nil {
w.Data = countDataByName(sourceName, deserializedData, t.Request.Filters, string(chart.Name))
}
out <- w
}
....
How to modify it, to avoid setting models.Noagg Model type in a strict way?
答案1
得分: 4
在运行时动态创建类型的实例可以使用 reflect 包来实现。你可以使用一个映射（map）来存储应该能够创建的不同类型：
示例代码：
package main
import (
"fmt"
"reflect"
)
type Foo struct {
Foo string
}
type Bar struct {
Bar int
}
func main() {
var sourceTypes = map[string]reflect.Type{
"foo": reflect.TypeOf(Foo{}),
"bar": reflect.TypeOf(Bar{}),
}
sourceName := "foo"
var deserializedData interface{}
deserializedData = reflect.New(sourceTypes[sourceName]).Interface()
fmt.Printf("%#v", deserializedData)
}
输出结果：
&main.Foo{Foo:""}
Playground: http://play.golang.org/p/qeDA4cu5et
英文:
Creating an instance of a type dynamically during runtime can be done using the reflect package. You can use a map to store the different types that you should be able to create:
Example:
package main
import (
"fmt"
"reflect"
)
type Foo struct {
Foo string
}
type Bar struct {
Bar int
}
func main() {
var sourceTypes = map[string]reflect.Type{
"foo": reflect.TypeOf(Foo{}),
"bar": reflect.TypeOf(Bar{}),
}
sourceName := "foo"
var deserializedData interface{}
deserializedData = reflect.New(sourceTypes[sourceName]).Interface()
fmt.Printf("%#v", deserializedData)
}
Output:
> &main.Foo{Foo:""}
Playground: http://play.golang.org/p/qeDA4cu5et
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