To create and insert a new instance of an Entity in the default context, you can use:
// Objective-C
Person *myPerson = [Person MR_createEntity];
// Swift
let myPerson = Person.mr_createEntity()
To create and insert an entity into specific context:
// Objective-C
Person *myPerson = [Person MR_createEntityInContext:otherContext];
// Swift
let myPerson = Person.mr_createEntity(in: otherContext)