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CRUD - C++ SDK

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

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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