如何將這個SQL查詢轉換到核心數據

Question

如何將SQL查詢轉換成謂語或提取請求，

select a.name 
from a 
group by a.name; 

Answer 1

這是一個可能的解決方案：

NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:@"a"]; 
[request setPropertiesToFetch:@[@"name"]]; 
[request setPropertiesToGroupBy:@[@"name"]]; 
[request setResultType:NSDictionaryResultType];