我正在构建一个应用程序，它可以从一个API中获取Warning个对象，我不控制这个API，他们也不想删除我正在try 解决的行为.
I would like to be able to parse either a single Warning object or a List<Warning> objects. (Because the API returns either 1 object if there is only 1 or > 1 a list of objects.)
Question
如何将对象直接解析为列表或使用Moshi解析列表？
The data I get looks either like this:
{
# List<Warning>
"warnings": [{...}, {...}]
}
或者像这样:
{
# Warning
"warnings": {...}
}
I have read and found some sources on this topic, but no examples and I am not sure how to proceed.. so any pointers would be highly appreciated.
Attempt
起初，我试图用鞋钉固定一个自动生成的moshi适配器，以为我可以在上面构建它，但我不知道发生了什么，所以它并没有真正把我带到任何地方.但我还是包含了生成的代码，以防它对任务仍然有用罢工>
Edit: This is what I currently have, though im not very pleased by the fact it takes an instance of Moshi to work.
Solution
Generalised approach with a Factory
I tried to port adapter which Eric wrote to kotlin since I since has realised that a more general approach is better much like Eric points out in his reply. As soon a this is working, I will re-write parts of this post to make it more understandable, its a bit messy now I apologize for that.
EDIT: I ended up using the solution Eric suggested in another thread but ported to Kotlin.
带工厂的适配器
class SingleToArrayAdapter(
val delegateAdapter: JsonAdapter<List<Any>>,
val elementAdapter: JsonAdapter<Any>
) : JsonAdapter<Any>() {
companion object {
val INSTANCE = SingleToArrayAdapterFactory()
}
override fun fromJson(reader: JsonReader): Any? =
if (reader.peek() != JsonReader.Token.BEGIN_ARRAY) {
Collections.singletonList(elementAdapter.fromJson(reader))
} else delegateAdapter.fromJson(reader)
override fun toJson(writer: JsonWriter, value: Any?) =
throw UnsupportedOperationException("SingleToArrayAdapter is only used to deserialize objects")
class SingleToArrayAdapterFactory : JsonAdapter.Factory {
override fun create(type: Type, annotations: Set<Annotation>, moshi: Moshi): JsonAdapter<Any>? {
val delegateAnnotations = Types.nextAnnotations(annotations, SingleToArray::class.java)
if (delegateAnnotations == null) return null
if (Types.getRawType(type) != List::class.java) throw IllegalArgumentException("Only lists may be annotated with @SingleToArray. Found: $type")
val elementType = Types.collectionElementType(type, List::class.java)
val delegateAdapter: JsonAdapter<List<Any>> = moshi.adapter(type, delegateAnnotations)
val elementAdapter: JsonAdapter<Any> = moshi.adapter(elementType)
return SingleToArrayAdapter(delegateAdapter, elementAdapter)
}
}
}
Qualifier
Note: I had to add the Target(FIELD).
@Retention(RUNTIME)
@Target(FIELD)
@JsonQualifier
annotation class SingleToArray
Usage
Annotate a field you want to make sure is parsed as a list with @SingleToArray.
data class Alert(
@SingleToArray
@Json(name = "alert")
val alert: List<Warning>
)
and dont forget to add the adapter to your moshi instance:
val moshi = Moshi.Builder()
.add(SingleToArrayAdapter.INSTANCE)
.build()