objective-c - 如何将此 sql 查询转换为 Core Data

Question

如何将 sql 查询转换为谓词或获取请求，

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];