coredata – 获取一个属性到一个数组中

目标：我想从数据库（核心数据）中获取一个属性（从一个实体）的值到一个数组中。

例

实体名称=员工

属性= employeeID

我只想将所有employeeID填充到数组/集合中。

题

下面给出的是我的实现，我只是觉得它是一种方式，我想知道是否有更好的方法来做到这一点。

码

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Employees"]; fetchRequest.resultType = NSDictionaryResultType; [fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"employeeID", nil]]; NSError *error = nil; NSArray *results = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; NSMutableArray *employeeIDs = [NSMutableArray array]; for(id currentRecord in results) { [employeeIDs addObject:[currentRecord objectForKey:@"employeeID"]]; } 

Answer 1

你可以避免最后的循环，

代替，

 NSMutableArray *employeeIDs = [NSMutableArray array]; for(id currentRecord in results) { [employeeIDs addObject:[currentRecord objectForKey:@"employeeID"]]; } 

尝试这个，

 NSMutableArray *employeeIDs = [results valueForKey:@"employeeID"]; 

Answer 2

一种做法是 –

 NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Employees"]; fetchRequest.resultType = NSDictionaryResultType; NSError *error = nil; NSArray *results = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; NSMutableArray *employeeIDs = [results valueForKey:@"employeeID"];