如何将这个SQL查询转换到核心数据

Question

如何将SQL查询转换成谓语或提取请求，

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

Answer 1

这是一个可能的解决方案：

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