objective-c - fetchRequestFromTemplateWithName 返回 nil

Question

我添加了 FETCH REQUESTS 并编写了以下代码。

NSFetchRequest *fetchRequest = [delegate.managedObjectModel 
   fetchRequestFromTemplateWithName:@"isUser" 
              substitutionVariables:nil];

但是 fetchRequest 返回 nil。帮帮我!

Answer 1

来自fetchRequestFromTemplateWithName: 的文档:

The variables dictionary must provide values for all the variables. If you want to test for a nil value, use [NSNull null].

NSFetchRequest *fetchRequest = [delegate.managedObjectModel 
  fetchRequestFromTemplateWithName:@"isUser" 
  substitutionVariables:[NSDictionary dictionaryWithObjectsAndKeys:
      @"type", [NSNull null], nil]];

也许您正在寻找无需替换变量即可工作的 fetchRequestTemplateForName:。