CRUD - Delete - C++ SDK

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Delete Realm Objects

Delete an Object
Delete an Inverse Relationship
Delete Map Keys/Values
Delete Set Values

Atlas Device SDKs are deprecated. Refer to the deprecation page for details.

Delete Realm Objects

Deleting Realm Objects must occur within write transactions. For more information about write trasactions, see: Write Transactions.

Delete an Object

To delete an object from a realm, pass the object to Realm.remove() function inside of a write transaction.

realm.write([&] { realm.remove(managedDog); });

Delete an Inverse Relationship

You can't delete an inverse relationship directly. Instead, an inverse relationship automatically updates by removing the relationship through the related object.

In this example, a Person has a to-one relationship to a Dog, and the Dog has an inverse relationship to Person. Setting the Person.dog relationship to nullptr removes the inverse relationship from the Dog object.

auto config = realm::db_config();
auto realm = realm::db(std::move(config));
auto dog = realm::Dog{.name = "Wishbone"};
auto [joe] = realm.write([&realm]() {
  auto person =
      realm::Person{.name = "Joe", .age = 27, .dog = nullptr};
  return realm.insert(std::move(person));
});
// Assign an object with an inverse relationship
// to automatically set the value of the inverse relationship
realm.write([&dog, joe = &joe]() { joe->dog = &dog; });
CHECK(joe.dog->owners.size() == 1);
// ... Later ...
// Removing the relationship from the parent object
// automatically updates the inverse relationship
realm.write([joe = &joe]() { joe->dog = nullptr; });
CHECK(realm.objects<realm::Dog>()[0].owners.size() == 0);

Model

This example uses the following model:

struct Dog;
struct Person {
  realm::primary_key<int64_t> _id;
  std::string name;
  int64_t age = 0;
  Dog* dog;
};
REALM_SCHEMA(Person, _id, name, age, dog)
struct Dog {
  realm::primary_key<int64_t> _id;
  std::string name;
  int64_t age = 0;
  linking_objects<&Person::dog> owners;
};
REALM_SCHEMA(Dog, _id, name, age, owners)

Delete Map Keys/Values

To delete a map key, pass the key name to erase():

realm.write([&] { tommy.locationByDay.erase("Tuesday"); });

Delete Set Values

You can delete a set element with erase(), or remove all elements from a set with clear().

// Remove an element from the set with erase()
auto it3064 = managedDocsRealm.openPullRequestNumbers.find(3064);
CHECK(it3064 != managedDocsRealm.openPullRequestNumbers.end());
realm.write([&] { managedDocsRealm.openPullRequestNumbers.erase(it3065); });
CHECK(managedDocsRealm.openPullRequestNumbers.size() == 4);
// Clear the entire contents of the set
realm.write([&] { managedDocsRealm.openPullRequestNumbers.clear(); });
CHECK(managedDocsRealm.openPullRequestNumbers.size() == 0);

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