我有以下課程：
public class RemoteService {
private static class QueryEntry<T> {
public final IQueryInput<T> input;
public final FutureCallback<T> callback;
// constructor not shown here
}
private final List<QueryEntry<?>> mQueries;
public <T> Result doStuff(IQueryInput<T> input, FutureCallback<T> callback) {
// Simplified code here
if(mIsServiceAlive) {
return actuallyMakeQuery(input, callback);
} else {
// will make it happen later
mQueries.add(new QueryEntry(input, callback));
}
}
private <T> Result actuallyMakeQuery(IQueryInput<T> input, FutureCallback<T> callback) {
// ... magic
return result;
}
//.. other code
private void onServiceAlive() {
//This method is called when this service is connected to dependencies
//and is now live. Here we want to actually make the queries ...
for(final QueryEntry<?> entry : mQueries) {
// Compile error here because I can't reference entry<T>.input
// as T is now lost .... is there any where I can make this happen?
actuallyMakeQuery(entry.input, entry.callback);
}
mQueries.clear();
}
}
這里的問題很簡單-> 無論如何我可以打電話actuallyMakeQuery嗎mQueries？我不這么認為，因為當我快取所有輸入時，我輸了，T因為mQueries正在使用QueryEntry<?>. 我也無法更改doStuff簽名，因為它被定義為其他地方的介面。我可以在這里做什么？
uj5u.com熱心網友回復：
您可以通過引入額外的間接級別來捕獲通配符：
private <T> Result actuallyMakeQuery(IQueryInput<T> input, FutureCallback<T> callback) {
// ... magic
return new Result();
}
private <T> Result actuallyMakeQuery(QueryEntry<T> entry) {
// no wildcards anymore
return actuallyMakeQuery(entry.input, entry.callback);
}
另外，您省略了<>in
mQueries.add(new QueryEntry<>(input, callback));
不必要地把它變成原始型別。
然后，您可以使用該新方法：
private void onServiceAlive() {
// This method is called when this service is connected to dependencies
// and is now live. Here we want to actually make the queries ...
for (final QueryEntry<?> entry : mQueries) {
// no problem here anymore
actuallyMakeQuery(entry);
}
mQueries.clear();
}
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