I have a simple data model:
class Dog: Object {
dynamic var Name : String = ""
let Colour = List<ColourItem>()
}
class ColourItem: Object {
dynamic var colourName = ""
}
And I can do NSPredicate searches for all Dogs, or Dogs with a specific colour assigned to them:
let importPredicate = NSPredicate(format: "%# IN Colour.colourName", colourVar)
let results = realm.objects(Dog).filter(importPredicate)
But I am stuck on how to search for just Dogs without any colour assigned to them. (i.e.: I want to filter for dogs whose Colour property is empty).
Any ideas/hints?
You can query for dogs with an empty Colour list like so:
let results = realm.objects(Dog.self).filter("Colour.#count == 0")
Related
Is it possible to use "NOT IN" in a NSPredicate with a SUBQUERY?
In a 'normal' NSPredicate, this works:
NSPredicate(format: "NOT (uid IN %#)", uids)
However, I'm trying this "NOT IN" syntax in a NSPredicate with SUBQUERY and it doesn't work (but doesn't crash either):
NSPredicate(format:"SUBQUERY(forests.treeFamily, $tree, NOT ($tree._id IN %#)) .#count > 0", arrayOfTreesIds)
While the following "IN" syntax works fine:
NSPredicate(format:"SUBQUERY(forests.treeFamily, $tree, $tree._id IN %#) .#count > 0", arrayOfTreesIds)
Any idea how I could achieve this?
UPDATED
The answer I got from Jay made me think I wasn't clear enough on the schema/class.
So let's make an example with dogs.
We have a ShelterClass, that has a property of Dogs. It's an array of Dog objects, to keep tracks of which dogs are hosted in the shelter.
The Dog class has a "race" property, which is a reference to a Race class.
I want to filter Shelters that DON'T have certain races of dogs.
While I would use this to filter Shelters that DO have certain races of dogs:
NSPredicate(format:"SUBQUERY(dogs.race, $race, $race._id IN %#) .#count > 0", arrayOfRaceIds)
I can't find how to filter out / use a "NOT IN" syntax.
Super easy! Here's the format for a regular filter
If you have a DogClass
class DogClass: Object {
#objc dynamic var name = ""
}
and then want a list of dogs that are not named Dino and Fido, here's the code
let dogNames = ["Fido", "Dino"]
let results = realm.objects(DogClass.self).filter("NOT dog_name IN %#", dogNames)
The result of a subquery is going to be dependent on what result you expect and what the subquery is for.
For example, let's say we have a PersonClass that has property of dogs, which is a list of dogs they know. If we want all persons that do not know Fido or Dino, this is the query
let personResults = realm.objects(PersonClass.self).filter("NOT ANY dogs.dog_name in %#", dogNames)
EDIT
Based on an updated question, let's try this. Since I used a PersonClass in the above I will pose this question.
I want a list of all of the people (Shelters) that do not have a breed (race)
of Hound. Here's the Breed class to track the breeds
class BreedClass: Object {
#objc dynamic var breed = ""
}
and the DogClass that has a breed property (like 'Race' in the question)
class DogClass: Object {
#objc dynamic var dog_id = NSUUID().uuidString
#objc dynamic var dog_name = ""
#objc dynamic var dog_breed: BreedClass?
override static func primaryKey() -> String? {
return "dog_id"
}
}
and then finally the Person class that has a List of DogClass objects
class PersonClass: Object {
#objc dynamic var person_id = UUID().uuidString
#objc dynamic var first_name = ""
let dogs = List<DogClass>()
override static func primaryKey() -> String? {
return "person_id"
}
}
Then we have some populated breed objects
let b0 = BreedClass()
b0.breed = "Mut"
let b1 = BreedClass()
b1.breed = "Poodle"
let b2 = BreedClass()
b2.breed = "Hound"
and then add breeds to the dogs and add the dogs to the persons. In this case we're only going to have one dog that's a b2, Hound
let d2 = DogClass()
d2.dog_name = "Sasha"
d2.dog_breed = b2
In this case I added 4 people, Bert, Ernie, Grover and The Count. Ernie was the only person I added the hound to.
Finally a query that will return all people that do NOT have a breed of Hound.
let breed = "Hound"
let personResults = realm.objects(PersonClass.self).filter("NOT ANY dogs.dog_breed.breed == %#", breed)
for person in personResults {
print(person.first_name)
}
and the output
Bert
Grover
The Count
And Ernie is missing because he has a Hound.
I'm trying to query multiple objects from Realm using a List of Primary Key Strings. I know I can do this using a for..in loop but I'd rather use a filter if possible.
primaryKeyArray contains a number of Strings
class Item : Object {
#objc dynamic var itemKey = NSUUID().uuidString
}
var primaryKeyArray : List<String>?
//Assume Realm DB already contains multiple Item Objects
//primaryKeyArray contains "key1", "key2", "key3", etc..
let predicate = NSPredicate(format: "itemKey == %#", primaryKeyArray)
let items = realm.objects(Item.self).filter(predicate)
I know the problem is with my predicate format. Not sure whether to use some form of CONTAINS or what? Any help with the predicate syntax would be greatly appreciated!
I think you are asking how to query Realm for items that have keys that match a set of keys in an array.
So given a DogClass Realm Object
class DogClass: Object {
#objc dynamic var dog_id = NSUUID().uuidString
#objc dynamic var dog_name = ""
override static func primaryKey() -> String? {
return "dog_id"
}
}
and suppose we know we want to retrieve three dogs that match some given primary keys
let keysToMatch = ["302AC133-3980-41F3-95E8-D3E7F639B769", "54ECC485-4910-44E5-98B9-0712BB99783E", "71FE403B-30CD-4E6C-B88A-D6FDBB08C509"]
let dogResults = realm.objects(DogClass.self).filter("dog_id IN %#", keysToMatch)
for dog in dogResults {
print(dog.dog_id, dog.dog_name)
}
Note the use of IN in the filter, which will match any dogs with id's in the given array.
You can also pass in a Realm List Object instead of a Swift array and get the same result.
let listOfKeysToMatch = List<String>()
listOfKeysToMatch.append("302AC133-3980-41F3-95E8-D3E7F639B769")
listOfKeysToMatch.append("54ECC485-4910-44E5-98B9-0712BB99783E")
listOfKeysToMatch.append("71FE403B-30CD-4E6C-B88A-D6FDBB08C509")
let dogResults2 = realm.objects(DogClass.self).filter("dog_id in %#", listOfKeysToMatch)
for dog in dogResults2 {
print(dog.dog_id, dog.dog_name)
}
let predicate = NSPredicate(format: "itemKey IN %#", primaryKeyArray)
This is how my Realm objects look:
class Restaurant: Object {
#objc dynamic var name: String? = nil
let meals = List<Meal>()
}
class Meal: Object {
#objc dynamic var mealName: String? = nil
let tag = RealmOptional<Int>()
}
I'm trying to fetch all meals that have some tags (I know I can filter all Realm objects of type Meal for specific tags), but the goal is to fetch all Restaurant objects and filter it's Meal child objects based on tag values.
I tried filtering like this:
restaurants = realm.objects(Restaurant.self).filter("meals.#tags IN %#", selectedTags)
but this won't work. Is there a way to filter results based on values in child object list?
To clarify the question, this is an example how filtering should work
for selectedTags = [1, 2, 3]
This is the whole Restaurant model that is saved in Realm.
[Restaurant {
name = "Foo"
meals = [
Meal {
mealName = "Meal 1"
tag = 1
},
Meal {
mealName = "Meal 2"
tag = 2
},
Meal {
mealName = "Meal 7"
tag = 7
}
]
}]
Filtering should return this:
[Restaurant {
name = "Foo"
meals = [
Meal {
mealName = "Meal 1"
tag = 1
},
Meal {
mealName = "Meal 2"
tag = 2
}
]
}]
Here's one possible solution - add a reverse refererence to the restaurant for each meal object
class Restaurant: Object {
#objc dynamic var name: String? = nil
let meals = List<Meal>()
}
class Meal: Object {
#objc dynamic var mealName: String? = nil
let tag = RealmOptional<Int>()
#objc dynamic var restaurant: Restaurant? //Add this
}
then query the meals for that restaurant with the tags you want.
let results = realm.objects(Meal.self).filter("restaurant.name == %# AND tag IN %#", "Foo", [1,2])
LinkingObjects could also be leveraged but it depends on what kind of queries will be needed and what the relationships are between Restaurants and Meals - I am assuming 1-Many in this case.
if you want ALL restaurants, then LinkingObjects is the way to go.
Edit:
Thought of another solution. This will work without adding a reference or an inverse relationship and will return an array of restaurants that have meals with the selected tags.
let selectedTags = [1,2]
let results = realm.objects(Restaurant.self).filter( {
for meal in $0.meals {
if let thisTag = meal.tag.value { //optional so safely unwrap it
if selectedTags.contains(thisTag) {
return true //the tag for this meal was in the list, return true
}
} else {
return false //tag was nil so return false
}
}
return false
})
In short, you cannot do what you are asking. Not within a Realm query (and therefore benefit from update notifications if that is important) at least. No doubt you can make some kind of structure containing what you want though via non-Realm filtering.
To better answer, let's first consider what you're trying to produce as a query result. As you say, your attempt above won't work. But you're trying to filter Restaurants by having some Meals matching some criteria; this is probably achievable, but your resulting query on Restaurant type would then produce a list of Restaurants. Each restaurant would still have a natural property of all its Meals, and would require the same filter applied again to the meals.
It makes sense though to add a function (if you need the search criteria to be dynamic, use a computed property if the filter is always the same tags) to the Restaurant class that produces a view of its Meals matching your criteria.
e.g.
extension Restaurant
{
var importantMeals : Results<Meal>
{
return meals.filter(...)
}
}
So I think there are two options.
Iterate through all Restaurant objects, and add it to a data structure of your own (Set or array) if its importantMeals property is not empty. Then use the same property to produce the meal list when needed. Or you could use a non-Realm filter to produce that query for you. E.g. realm.objects(Restaurant.self).compactMap {$0}.filter { !$0.importantMeals.isEmpty }
Alternatively, filter all Meals according to your criteria (realm.objects(Meal.self).filter(...)). You could then add a LinkingObjects property to your Meal class to make the Set of Restaurants with relevant Meals.
The correct approach will depend on how you want to use the results, but I'd suggest approach 1 will see you right. Note that you might want to sort the results produced by queries before using if order is of any importance to you (e.g. for displaying in UITableView) as there is no guarantee that the order of objects will be the same for each query performed.
I have the following Realm Objects
class Patient: Object {
#objc dynamic var name: String?
let list = List<RString>()
}
class RString: Object {
#objc dynamic var stringValue: String?
}
I need to filter Patient objects that have an RString component in List with stringValue = "test"
Is something like this possible?
patients = realm?.objects(Patient.self).filter("name = 'name1' AND #% IN list", RString(stringValue: 'test'))
You need to use a SUBQUERY to be able to access the properties of the elements of a List in an NSPredicate. The SUBQUERY will evaluate true for every Patient whose list property includes at least 1 RString element whose stringValue matches the provided String.
patients = realm?.objects(Patient.self).filter("name = %# AND SUBQUERY(list,$element,$element.stringValue == %#).#count>0", "name1", "test")
Wondering if anyone have faced & solved this issue:
Description
I have 2 Classes called Person & Dog where a person can have more than one dog.
class Dog: Object {
dynamic var name = ""
dynamic var age = 0
}
class Person: Object {
dynamic var name = ""
dynamic var picture: NSData? = nil // optionals supported
let dogs = List<Dog>()
}
According to my requirement, I need to fetch all objects from person.name == "ABC" & apply sort all dogs by Name.
Snippet:
let realm = try! Realm()
let result = realm.objects(Person.self).filter("name == %#","ABC").sorted(property : "name")
From the above snippet, sorting is done based on the person Name not on the dog's Name.
How to create a filter & sort the list by dog name?
realm.objects(Person.self) returns Results<Person>. Calling sorted() to Results<Person> means sort Person. If you'd like to sort dogs, you can retrieve element of person first, (e.g. let person = result[0]), then retrieve dogs property, call sorted() method to it.
let people = realm.objects(Person.self).filter("name == %#","ABC")
let person = people.first!
let sortedDogs = person.dogs.sorted(property : "name")