Use async/await for utils

Author: jamesots

lib/src/utils.dart

@@ -6,50 +6,30 @@ part of utils;
 class TableDropper {
   ConnectionPool pool;
   List<String> tables;
-  List<String> _tables = [];
-  
+
   /**
    * Create a [TableDropper]. Needs a [pool] and
    * a list of [tables].
    */
   TableDropper(this.pool, this.tables);
 
-  void _dropTables(Completer c) {
-    afterDrop() {
-      if (_tables.length == 0) {
-        c.complete(null);
-      } else {
-        _dropTables(c);
-      }
-    }
-    
-    var table = _tables.removeAt(0);
-    pool.query('drop table $table')
-      // if it's an unknown table, ignore the error and continue
-      .then((_) {
-        afterDrop();
-      })
-      .catchError((e) {
-        afterDrop();
-      }, test: (e) => e is MySqlException && (e as MySqlException).errorNumber == ERROR_UNKNOWN_TABLE)
-      .catchError((e) {
-        c.completeError(e);
-      });
-  }
-
   /**
    * Drops the tables this [TableDropper] was created with. The 
    * returned [Future] completes when all the tables have been dropped.
    * If a table doesn't exist, it is ignored.
-   * 
-   * Do not run this a second time until the future has completed.
    */
-  Future dropTables() {
-    var c = new Completer();
-    _tables.clear();
-    _tables.addAll(tables);
-    _dropTables(c);
-    return c.future;
+  Future dropTables() async {
+    await Future.forEach(tables, (table) async {
+      try {
+        await pool.query('drop table $table');
+      } catch (e) {
+        if (e is MySqlException && (e as MySqlException).errorNumber == ERROR_UNKNOWN_TABLE) {
+          // if it's an unknown table, ignore the error and continue
+        } else {
+          throw e;
+        }
+      }
+    });
   }
 }
 
@@ -60,40 +40,21 @@ class TableDropper {
 class QueryRunner {
   final ConnectionPool pool;
   final List<String> queries;
-  final List<String> _queries = [];
-  
+
   /**
    * Create a [QueryRunner]. Needs a [pool] and
    * a list of [queries]. 
    */
   QueryRunner(this.pool, this.queries);
 
-  Future _executeQueries(Completer c) {
-    var query = _queries.removeAt(0);
-    pool.query(query).then((result) {
-      if (_queries.length == 0) {
-        c.complete(null);
-      } else {
-        _executeQueries(c);
-      }
-    })
-    .catchError((e) {
-      c.completeError(e);
-    });
-  }
-
   /**
    * Executes the queries this [QueryRunner] was created with. The
    * returned [Future] completes when all the queries have been executed.
    * Results are ignored.
-   * 
-   * Do not run this a second time until the future has completed.
    */
-  Future executeQueries() {
-    var c = new Completer();
-    _queries.clear();
-    _queries.addAll(queries);
-    _executeQueries(c);
-    return c.future;
+  Future executeQueries() async {
+    await Future.forEach(queries, (query) async {
+      await pool.query(query);
+    });
   }
 }