refactor db disposables

spec/std/db/dummy_driver.cr

@@ -29,7 +29,7 @@ class DummyDriver < DB::Driver
       0
     end
 
-    def perform_close
+    protected def do_close
     end
   end
 
@@ -57,6 +57,9 @@ class DummyDriver < DB::Driver
         @params[index] = arg
       end
     end
+
+    protected def do_close
+    end
   end
 
   class DummyResultSet < DB::ResultSet
@@ -69,6 +72,9 @@ class DummyDriver < DB::Driver
       @@last_result_set = self
     end
 
+    protected def do_close
+    end
+
     def self.last_result_set
       @@last_result_set.not_nil!
     end

src/db/connection.cr

@@ -15,30 +15,11 @@ module DB
   # Also override `#last_insert_id` to allow safe access to the last inserted id through this connection.
   #
   abstract class Connection
-    @closed = false
+    include Disposable
-
-    # Closes this connection.
-    def close
-      return if @closed
-      @closed = true
-      perform_close
-    end
-
-    # Returns `true` if this connection is closed. See `#close`.
-    def closed?
-      @closed
-    end
-
-    # :nodoc:
-    def finalize
-      close unless closed?
-    end
 
     # :nodoc:
     abstract def prepare(query) : Statement
 
     include QueryMethods
-
-    protected abstract def perform_close # TODO do_close
   end
 end

src/db/db.cr

@@ -99,6 +99,7 @@ module DB
 end
 
 require "./query_methods"
+require "./disposable"
 require "./database"
 require "./driver"
 require "./connection"

src/db/disposable.cr

@@ -0,0 +1,28 @@
+module DB
+  # Generic module to encapsulate disposable db resources.
+  module Disposable
+    macro included
+      @closed = false
+    end
+
+    # Closes this object.
+    def close
+      return if @closed
+      @closed = true
+      do_close
+    end
+
+    # Returns `true` if this object is closed. See `#close`.
+    def closed?
+      @closed
+    end
+
+    # :nodoc:
+    def finalize
+      close
+    end
+
+    # Implementors overrides this method to perform resource cleanup
+    protected abstract def do_close
+  end
+end

src/db/result_set.cr

@@ -13,6 +13,8 @@ module DB
   # 4. Override `#column_count`, `#column_name`.
   # 5. Override `#column_type`. It must return a type in `DB::TYPES`.
   abstract class ResultSet
+    include Disposable
+
     getter statement
 
     def initialize(@statement : Statement)
@@ -27,26 +29,6 @@ module DB
       end
     end
 
-    # Closes this result set.
-    def close
-      return if @closed
-      @closed = true
-      do_close
-    end
-
-    # Returns `true` if this result set is closed. See `#close`.
-    def closed?
-      @closed
-    end
-
-    # :nodoc:
-    def finalize
-      close
-    end
-
-    protected def do_close
-    end
-
     # Move the next row in the result.
     # Return `false` if no more rows are available.
     # See `#each`

src/db/statement.cr

@@ -10,13 +10,13 @@ module DB
   # 4. `#perform_exec` executes a query that is expected to return an `ExecResult`
   # 6. `#do_close` is called to release the statement resources.
   abstract class Statement
+    include Disposable
+
     getter connection
 
     def initialize(@connection)
-      @closed = false
     end
 
-
     # See `QueryMethods#exec`
     def exec
       perform_exec(Slice(Any).new(0)) # no overload matches ... with types Slice(NoReturn)
@@ -82,27 +82,7 @@ module DB
       perform_query(args.to_a.to_unsafe.to_slice(args.size))
     end
 
-    # Closes this statement.
-    def close
-      return if @closed
-      @closed = true
-      do_close
-    end
-
-    # Returns `true` if this statement is closed. See `#close`.
-    def closed?
-      @closed
-    end
-
-    # :nodoc:
-    def finalize
-      close
-    end
-
     protected abstract def perform_query(args : Slice(Any)) : ResultSet
     protected abstract def perform_exec(args : Slice(Any)) : ExecResult
-
-    protected def do_close
-    end
   end
 end