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<Section> *sections;
@property (nonatomic, strong) RLMArray<User> *users;

@end

@interface Section : RLMObject

@property NSString *name;
@property BOOL isCollapsed;
@property RLMArray<User> *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);
}

来源：https://stackoverflow.com/questions/38890556/subquery-and-in-statement-in-realm

标签

ios

objective-c

realm