Subquery and IN Statement in realm

问题:

I have three realm objects. Department, section and user. section is a kind of sub department in a department. But there will be users under each section and each department.

@interface Department : RLMObject  @property NSString *name; @property BOOL isCollapsed;  @property (nonatomic, strong) RLMArray
 *sections; @property (nonatomic, strong) RLMArray *users;  @end  @interface Section : RLMObject  @property NSString *name; @property BOOL isCollapsed; @property RLMArray *users;  @end   @interface User : RLMObject  @property NSString *department; @property NSString *email; @property NSString *firstname; @property NSString *lastname; @property NSString *fullname;  @end 

What i want to do is, I want to search all the user whose first name and last name contains "a" and linked with department and section.

Now what i am doing is

searchText = [searchText lowercaseString];  RLMResults *sections = [Section objectsWhere:                         [NSString stringWithFormat:@"SUBQUERY(users, $user, $user.fullname contains '%@' OR $user.nickname contains '%@').@count > 0",searchText,searchText]];  NSMutableArray *sectionNames = [NSMutableArray array];  for (Section *section in sections) {     [sectionNames addObject:section.name]; }  NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(sections, $section, $section.name IN %@).@count > 0", sectionNames];  RLMResults *filteredDepartments = [[Department objectsWithPredicate:predicate] sortedResultsUsingProperty:@"name" ascending:YES];  NSPredicate *pred = [NSPredicate predicateWithFormat:@"SUBQUERY(users, $user, $user.fullname contains %@ OR $user.nickname contains %@).@count > 0",searchText,searchText]; RLMResults *departments = [filteredDepartments objectsWithPredicate:pred]; 

Right now the issue is there is two sections in sections array but in the deparments results, it returns null. please help. thanks.

Note: If one user already belongs to section then that user will not be include in department.

回答1:

Maybe you do not need to use subquery. More simply, you can use ANY in query like the following:

[Department objectsWhere:     @"ANY users.firstname CONTAINS %@ OR ANY users.lastname CONTAINS %@ OR ANY sections.users.firstname CONTAINS %@ OR ANY sections.users.lastname CONTAINS %@", searchText, searchText, searchText, searchText]; 

But I think using inverse relationships is more easier. In Realm, inverse relationships is defined with RLMLinkingObjects. You can add inverse relationships to User class as follows:

@interface User : RLMObject  ...  @property (readonly) RLMLinkingObjects *departments; @property (readonly) RLMLinkingObjects *sections;  @end  @implementation User  + (NSDictionary *)linkingObjectsProperties {     return @{@"departments": [RLMPropertyDescriptor descriptorWithClass:Department.class propertyName:@"users"],              @"sections": [RLMPropertyDescriptor descriptorWithClass:Section.class propertyName:@"users"]}; }  @end 

Then you can get departments and sections where the user belongs to from User's property, like the following:

RLMResults *users = [User objectsWhere:@"firstname CONTAINS %@ OR lastname CONTAINS %@" , searchText, searchText]; for (User *user in users) {     NSLog(@"%@", user.departments);     NSLog(@"%@", user.sections); } 

文章来源: Subquery and IN Statement in realm