在Objective-C中是否有类似于LINQ的东西？ [英] Is there something similar to LINQ in Objective-C?

问题描述

我想知道是否可能（以及如何）在Objective-C中提供类似以下的类：

I wonder if it is possible (and how) to provide a class in Objective-C with something like:

Person.Select(@"Name").OrderAsc(@"Name").Where(@"Id").EqualTo(1).And(@"Id").NotEqualTo(2).Load<Array>

这对于我正在做的项目非常方便。

That could be very handy for a project I'm doing.

我喜欢这种Django& SubSonic。

I like this way of coding present in Django & SubSonic.

推荐答案

简短的回答是，没有一个等价于Linq的Objective-C，但你可以混合SQLite，NSPredicate和CoreData调用在根据您的喜好的包装类中。您可能会对核心数据指南感兴趣， 谓词指南和此示例代码。

The short answer is that there is not an equivalent to Linq for Objective-C but you can fake it with a mix of SQLite, NSPredicate and CoreData calls in a wrapper class shaped to your liking. You'd probably be interested in the core data guide, the predicate guide, and this example code.

从上面的谓词指南：

NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Employee"
        inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// assume salaryLimit defined as an NSNumber variable
NSPredicate *predicate = [NSPredicate predicateWithFormat:
        @"salary > %@", salaryLimit];
[request setPredicate:predicate];
NSError *error = nil;
NSArray *array = [managedObjectContext executeFetchRequest:request error:&error];

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