Realm オブジェクトの削除 - Kotlin SDK

// Open a write transaction
realm.write {
    // Query the Frog type and filter by primary key value
    val frogToDelete: Frog = query<Frog>("_id == $0", PRIMARY_KEY_VALUE).find().first()
    // Pass the query results to delete()
    delete(frogToDelete)
}

// Open a write transaction
realm.write {
    // Query by species and limit to 3 results
    val bullfrogsToDelete: RealmResults<Frog> = query<Frog>("species == 'bullfrog' LIMIT(3)").find()
    // Pass the query results to delete()
    delete(bullfrogsToDelete)
}

// Open a write transaction
realm.write {
    // Query Frog type with no filter to return all frog objects
    val frogsLeftInTheRealm = query<Frog>().find()
    // Pass the query results to delete()
    delete(frogsLeftInTheRealm)
}

// Open a write transaction
realm.write {
    // Delete all objects from the realm
    deleteAll()
}

realm.write {
    // Query for the parent frog object with ponds
    val frog = query<Frog>("name == $0", "Kermit").find().first()
    val ponds = frog.favoritePonds
    // Iterate over the list and delete each pond object
    if (ponds.isNotEmpty()) {
        ponds.forEach { pond ->
            delete(pond)
        }
    }
    // Delete the parent frog object
    val frogToDelete = findLatest(frog)
    if (frogToDelete != null) {
        delete(frogToDelete)
    }
}

// Delete the parent object
realm.write {
    val businessToDelete = query<Business>("name == $0", "Big Frog Corp.").find().first()
    // Delete the parent object (deletes all embedded objects)
    delete(businessToDelete)
}

// Delete an embedded object directly
realm.write {
    val addressToDelete = query<EmbeddedAddress>("street == $0", "456 Lily Pad Ln").find().first()
    // Delete the embedded object (nullifies the parent property)
    delete(addressToDelete)
}
// Delete an embedded object through the parent
realm.write {
    val propertyToClear = query<Contact>("name == $0", "Kermit").find().first()
    // Clear the parent property (deletes the embedded object instance)
    propertyToClear.address = null
}

// Open a write transaction
realm.write {
    // Query for the parent forest object
    val forest = query<Forest>("name == $0", "Hundred Acre Wood").find().first()
    val forestPonds = forest.nearbyPonds
    assertEquals(5, forestPonds.size)
    // Remove the first pond in the list
    val removeFirstPond = forestPonds.first()
    forestPonds.remove(removeFirstPond)
    assertEquals(4, forestPonds.size)
    // Remove the pond at index 2 in the list
    forestPonds.removeAt(2)
    assertEquals(3, forestPonds.size)
    // Remove the remaining three ponds in the list
    forestPonds.removeAll(forestPonds)
    assertEquals(0, forestPonds.size)
}

// Open a write transaction
realm.write {
    val forest = query<Forest>("name == $0", "Hundred Acre Wood").find().first()
    val forestPonds = forest.nearbyPonds
    assertEquals(5, forestPonds.size)
    // Clear all ponds from the list
    forestPonds.clear()
    assertEquals(0, forestPonds.size)
}

// Open a write transaction
realm.write {
    // Query for the parent frog object
    val myFrog = query<RealmSet_Frog>("name == $0", "Kermit").find().first()
    val snackSet = myFrog.favoriteSnacks
    assertEquals(3, snackSet.size)
    // Remove one snack from the set
    snackSet.remove(snackSet.first { it.name == "Flies" })
    assertEquals(2, snackSet.size)
    // Remove the remaining two snacks from the set
    val allSnacks = findLatest(myFrog)!!.favoriteSnacks
    snackSet.removeAll(allSnacks)
    assertEquals(0, snackSet.size)
}

realm.write {
    val myFrog = realm.query<RealmSet_Frog>("name == $0", "Kermit").find().first()
    val snackSet = findLatest(myFrog)!!.favoriteSnacks
    assertEquals(3, snackSet.size)
    // Clear all snacks from the set
    snackSet.clear()
    assertEquals(0, snackSet.size)
}

// Find frogs who have forests with favorite ponds
val thisFrog = realm.query<Frog>("favoritePondsByForest.@count > 1").find().first()
// Set an optional value for a key to null if the key exists
if (thisFrog.favoritePondsByForest.containsKey("Hundred Acre Wood")) {
    realm.write {
        val mutableFrog = findLatest(thisFrog)
        if (mutableFrog != null) {
            mutableFrog.favoritePondsByForest["Hundred Acre Wood"] = null
        }
    }
}
realm.write {
    // Remove a key and its value
    findLatest(thisFrog)?.favoritePondsByForest?.remove("Lothlorien")
    // Remove all keys and values
    findLatest(thisFrog)?.favoritePondsByForest?.clear()
    assertTrue(thisFrogUpdated.favoritePondsByForest.isEmpty())
}