com.squareup.sqldelight.Query.kt Maven / Gradle / Ivy

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/*
 * Copyright (C) 2018 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.squareup.sqldelight

import com.squareup.sqldelight.db.SqlPreparedStatement
import com.squareup.sqldelight.db.SqlResultSet
import com.squareup.sqldelight.db.use
import com.squareup.sqldelight.internal.QueryList

/**
 * A listenable, typed query generated by SQLDelight.
 *
 * @param RowType the type that this query can map it's result set to.
 */
open class Query(
  private val statement: SqlPreparedStatement,
  private val queries: QueryList,
  private val mapper: (SqlResultSet) -> RowType
) {
  private val listeners = mutableSetOf()

  /**
   * Notify listeners that their current result set is staled.
   *
   * Called internally by SQLDelight when it detects a possible staling of the result set. Emits
   * some false positives but never misses a true positive.
   */
  fun notifyResultSetChanged() {
    synchronized(listeners) {
      listeners.forEach(Listener::queryResultsChanged)
    }
  }

  /**
   * Register a listener to be notified of future changes in the result set.
   */
  fun addListener(listener: Listener) {
    synchronized(listeners) {
      if (listeners.isEmpty()) queries.addQuery(this)
      listeners.add(listener)
    }
  }

  fun removeListener(listener: Listener) {
    synchronized(listeners) {
      listeners.remove(listener)
      if (listeners.isEmpty()) queries.removeQuery(this)
    }
  }

  /**
   * Execute [statement] as a query.
   */
  fun execute() = statement.executeQuery()

  /**
   * Execute [statement] and return the result set as a list of [RowType].
   */
  fun executeAsList(): List {
    val result = mutableListOf()
    execute().use {
      while (it.next()) result.add(mapper(it))
    }
    return result
  }

  /**
   * Execute [statement] and return the only row of the result set as a non null [RowType].
   *
   * @throws NullPointerException if when executed this query has no rows in its result set.
   * @throws IllegalStateException if when executed this query has multiple rows in its result set.
   */
  fun executeAsOne(): RowType {
    return executeAsOneOrNull()
        ?: throw NullPointerException("ResultSet returned null for $statement")
  }

  /**
   * Execute [statement] and return the first row of the result set as a non null [RowType] or null
   * if the result set has no rows.
   *
   * @throws IllegalStateException if when executed this query has multiple rows in its result set.
   */
  fun executeAsOneOrNull(): RowType? {
    execute().use {
      if (!it.next()) return null
      val item = mapper(it)
      if (it.next()) {
        throw IllegalStateException("ResultSet returned more than 1 row for $statement")
      }
      return item
    }
  }

  interface Listener {
    fun queryResultsChanged()
  }
}