从密钥路径恢复NSEntityDescription

Question

假设我有核心数据实体a和B，其中B通过属性a指向A。

给定B的NSEntityDescription，以及A的给定属性的密钥路径(例如@"a.name")，有没有办法恢复A的NSEntityDescription？

谢谢,

时间

Answer 1

我通过自己解析密钥路径成功地做到了这一点：

    // Split the path to the section name up
    NSArray *keyNameParts = [sectionNameKeyPath componentsSeparatedByString:@"."];

    // Follow this back to the Entity description for the Section Entity
    for (int idx = 0; idx < keyNameParts.count - 1; idx++) {
        NSDictionary *relationships = entityDescription.relationshipsByName;
        NSString *partName = [keyNameParts objectAtIndex:idx];
        NSRelationshipDescription *relationshipDescription = [relationships objectForKey:partName];
        if (!relationshipDescription)
        {
            [NSException raise:@"Relationship not found for keypath"
                        format:@"Entity '%@' does not point to a relationshop for '%@' in keypath '@'.", entityName, partName, sectionNameKeyPath];
        }
        entityDescription = relationshipDescription.entity;
    } 

如果有更直接的方法，我很想知道。