golang如何访问界面字段 [英] golang how to access interface fields
问题描述
我有一个如下的函数,用于解码一些json数据并将其作为接口返回。
I have a function as below which decodes some json data and returns it as an interface
package search
func SearchItemsByUser(r *http.Request) interface{} {
type results struct {
Hits hits
NbHits int
NbPages int
HitsPerPage int
ProcessingTimeMS int
Query string
Params string
}
var Result results
er := json.Unmarshal(body, &Result)
if er != nil {
fmt.Println("error:", er)
}
return Result
}
我试图访问数据字段(例如Params),但由于某些原因说界面没有这样的领域。任何想法为什么?
I'm trying to access the data fields ( e.g. Params) but for some reasons it says that the interface has no such field. Any idea why ?
func test(w http.ResponseWriter, r *http.Request) {
result := search.SearchItemsByUser(r)
fmt.Fprintf(w, "%s", result.Params)
$ b $一个接口变量可用于存储符合接口的任何值,并调用该接口的艺术部分的方法。
请注意,您将无法通过接口变量访问底层值上的字段。
In this case, your SearchItemsByUser
method returns an interface{}
value (i.e. the empty interface), which can hold any value but doesn't provide any direct access to that value. You can extract the dynamic value held by the interface variable through a type assertion, like so:
在这种情况下,您的 SearchItemsByUser
方法返回一个接口{}
值(即空接口),它可以保存任何值,但不提供对该值的任何直接访问。您可以通过类型断言来提取接口变量所拥有的动态值,如下所示:
dynamic_value := interface_variable.(typename)
Except that in this case, the type of the dynamic value is private to your SearchItemsByUser method. I would suggest making two changes to your code:
除此之外,动态值的类型对您的SearchItemsByUser方法是私有的。我建议对您的代码进行两处更改:
Define your
results
type at the top level, rather than within the method body.
-
定义您的
结果
类型在顶层,而不是在方法体内。 使
结果
类型的值,而不是界面{}
。Make SearchItemsByUser
directly return a value of the results
type instead of interface{}
.
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