使用coredata中的代码创建两个实体之间的关系iPhone

Question

同时在代码中创建ManageObjectModel我创建两个实体及其属性。但问题是我如何能够创建关系到两个实体之间的许多关系。我的代码如下。 我只是想使用代码在两个员工和组织实体之间建立一对多的关系。

- (NSManagedObjectModel *)managedObjectModel 
{ 
    if (__managedObjectModel != nil) { 
     return __managedObjectModel; 
    } 

    __managedObjectModel = [[NSManagedObjectModel alloc] init]; 

    NSEntityDescription *employeeEntity = [[NSEntityDescription alloc] init]; 
    [employeeEntity setName:@"Employee"]; 
    [employeeEntity setManagedObjectClassName:@"Employee"]; 

    NSEntityDescription *organizationEntity = [[NSEntityDescription alloc] init]; 
    [organizationEntity setName:@"Organization"]; 
    [organizationEntity setManagedObjectClassName:@"Organization"]; 
    [__managedObjectModel setEntities:[NSArray arrayWithObjects:employeeEntity, organizationEntity, nil]]; 

    NSAttributeDescription *nameAttribute = [[NSAttributeDescription alloc] init];  
    [nameAttribute setName:@"name"]; 
    [nameAttribute setAttributeType:NSDateAttributeType]; 
    [nameAttribute setOptional:NO];  

    NSAttributeDescription *idAttribute = [[NSAttributeDescription alloc] init];  
    [idAttribute setName:@"id"]; 
    [idAttribute setAttributeType:NSInteger32AttributeType]; 
    [idAttribute setOptional:NO]; 

    NSArray *properties = [NSArray arrayWithObjects: nameAttribute, idAttribute, nil]; 
    [employeeEntity setProperties:properties]; 

    NSAttributeDescription *organizationNameAttribute = [[NSAttributeDescription alloc] init]; 
    [organizationNameAttribute setName:@"Name"]; 
    [organizationNameAttribute setAttributeType:NSStringAttributeType]; 
    [organizationNameAttribute setOptional:NO];   

    properties = [NSArray arrayWithObjects:organizationNameAttribute, nil]; 
    [organizationEntity setProperties:properties]; 

    return __managedObjectModel; 
} 

Answer 1

如果你真的想这样做的代码，你必须创建一个NSRelationshipDescription，并把它添加到源对象的属性。

这里是doc。

在分配对象之前创建对象并调用setMaxCount:。如果你看一下在isToMany方法的文档，你会看到，它说：

YES if the receiver represents a to-many relationship (its maxCount is greater than 1) otherwise NO.