diff --git a/samples/gtk_keep_wrapper.cr b/samples/gtk_keep_wrapper.cr
new file mode 100644
index 00000000..14653c7f
--- /dev/null
+++ b/samples/gtk_keep_wrapper.cr
@@ -0,0 +1,42 @@
+require "../src/gtk/autorun"
+
+class MyWidget < Gtk::Button
+  @foo : Int32?
+
+  def instantiate
+    self.label = "Default Label"
+    @foo = MyWidget.next_foo
+
+    keep_wrapper
+  end
+
+  @@foo = -1
+  def self.next_foo
+    @@foo += 1
+  end
+
+  def foo
+    @foo
+  end
+end
+
+w = Gtk::Window.new
+w.add v=Gtk::VBox.new(false,0)
+
+3.times do |i|
+  v.pack_start(mw=MyWidget.new, false, false, 1)
+
+  mw.label = "button#{i}"
+  
+  mw.on_clicked do |b|
+    p b.as(MyWidget).foo
+    v.foreach do |c| p c.as(MyWidget).foo end
+  end
+end
+
+v.foreach do |c| p c end
+
+w.connect "delete-event", ->Gtk.main_quit
+
+w.show_all
+
diff --git a/samples/gtk_subclasses.cr b/samples/gtk_subclasses.cr
index 736f8360..b167200d 100644
--- a/samples/gtk_subclasses.cr
+++ b/samples/gtk_subclasses.cr
@@ -1,13 +1,7 @@
 require "../src/gtk"
 
 class MyWindow < Gtk::ApplicationWindow
-  def self.new(app : Gtk::Application)
-    super
-  end
-
-  def initialize(ptr)
-    super(ptr)
-
+  def instantiate
     self.border_width = 10
     self.title = "Hello"
     add Gtk::Label.new("Hello")
@@ -15,13 +9,7 @@ class MyWindow < Gtk::ApplicationWindow
 end
 
 class MyApp < Gtk::Application
-  def self.new(id, flags : Gio::ApplicationFlags)
-    super
-  end
-
-  def initialize(ptr)
-    super(ptr)
-
+  def instantiate
     on_activate do |application|
       window = MyWindow.new(self)
       window.connect "destroy", &->quit
@@ -31,4 +19,4 @@ class MyApp < Gtk::Application
 end
 
 app = MyApp.new("org.crystal.mysample", :flags_none)
-app.run
\ No newline at end of file
+app.run
diff --git a/src/g_i_repository/info/callable_info.cr b/src/g_i_repository/info/callable_info.cr
index c6095e87..2b51519f 100644
--- a/src/g_i_repository/info/callable_info.cr
+++ b/src/g_i_repository/info/callable_info.cr
@@ -19,7 +19,7 @@ module GIRepository
       end
 
       def convert_to_crystal(variable)
-        "#{@definition}.new(#{variable})"
+        "#{@definition}.cast(#{variable})"
       end
 
       def convert_from_crystal(variable)
diff --git a/src/g_i_repository/info/function_info.cr b/src/g_i_repository/info/function_info.cr
index 285bf412..39eb7f82 100644
--- a/src/g_i_repository/info/function_info.cr
+++ b/src/g_i_repository/info/function_info.cr
@@ -60,8 +60,11 @@ module GIRepository
         io << "\n#{indent}  GLib::Error.assert __error" if throws?
 
         unless skip_return?
-          io << "\n#{indent}  #{"cast " if constructor?}#{return_type.convert_to_crystal("__return_value")}"
+          io << "\n#{indent} ins=#{"cast " if constructor?}#{return_type.convert_to_crystal("__return_value")}"
           io << " if __return_value" if may_return_null?
+          io << "\n#{indent} ins"
+          io << ".as(self)" if constructor?
+          io << " if __return_value" if may_return_null?          
           io << '\n'
         else
           io << "\n#{indent}  nil\n"
diff --git a/src/g_i_repository/info/type_info.cr b/src/g_i_repository/info/type_info.cr
index 4be19c3c..57d28cfc 100644
--- a/src/g_i_repository/info/type_info.cr
+++ b/src/g_i_repository/info/type_info.cr
@@ -101,7 +101,9 @@ module GIRepository
       when LibGIRepository::TypeTag::INTERFACE
         interface = self.interface
         case interface
-        when ObjectInfo, StructInfo, UnionInfo
+        when ObjectInfo
+          "#{interface.full_constant}.cast(#{variable})"
+        when StructInfo, UnionInfo
           "#{interface.full_constant}.new(#{variable})"
         else
           variable
@@ -128,7 +130,7 @@ module GIRepository
     def convert_from_crystal(variable)
       case tag
       when LibGIRepository::TypeTag::INTERFACE
-        pointer? ? "#{variable}.to_unsafe.as(Lib#{interface.full_constant}*)" : variable
+        pointer? ? "#{variable}.void_pointer.as(Lib#{interface.full_constant}*)" : variable
       when LibGIRepository::TypeTag::ARRAY,
            LibGIRepository::TypeTag::GLIST,
            LibGIRepository::TypeTag::GSLIST,
diff --git a/src/g_i_repository/wrapper_generator.cr b/src/g_i_repository/wrapper_generator.cr
index ec8c1b32..ca27db33 100644
--- a/src/g_i_repository/wrapper_generator.cr
+++ b/src/g_i_repository/wrapper_generator.cr
@@ -7,13 +7,13 @@ module GIRepository
     def write_constructor(libname, io, indent="")
       io.puts "#{indent}  @pointer : Void*"
       io.puts "#{indent}  def initialize(pointer : #{ptr_type(libname)})"
-      io.puts "#{indent}    @pointer = pointer.as(Void*)"
+      io.puts "#{indent}    @pointer = pointer.as(Void*)"         
       io.puts "#{indent}  end"
       io.puts
     end
 
     def write_to_unsafe(libname, io, indent="")
-      io.puts "#{indent}  def to_unsafe"
+      io.puts "#{indent}  def to_unsafe : #{ptr_type(libname)}"
       io.puts "#{indent}    @pointer.not_nil!.as(#{ptr_type(libname)})"
       io.puts "#{indent}  end"
       io.puts
diff --git a/src/g_object/wrapped.cr b/src/g_object/wrapped.cr
new file mode 100644
index 00000000..b655f9b4
--- /dev/null
+++ b/src/g_object/wrapped.cr
@@ -0,0 +1,102 @@
+module GObject
+  module WrappedType
+    GOBJECT_IS_WRAPPED_TAG = "__crystal_gobject_wrapper_id__"
+
+    @@n_wrapped            = UInt64.new(-1)
+    @@wrapped              = Hash(UInt64?, GObject::WrappedType?).new
+
+    def self.set_wrapped(ins)
+      @@n_wrapped += 1
+
+      ins.set_data_full(GOBJECT_IS_WRAPPED_TAG, Pointer(UInt64).new(@@n_wrapped+1).as(Void*), ->(d : Void*){
+        GObject::WrappedType.unwrap(d.address-1)
+        nil
+      })
+
+      @@n_wrapped
+    end
+
+    def self.keep_wrapper(ins)
+      if ins.has_wrapper?
+        id = ins.wrapper_id
+      else
+        id = set_wrapped ins
+      end
+
+      @@wrapped[id] = ins
+    end
+
+    def self.unwrap(id : UInt64)
+      @@wrapped.delete id
+    end
+
+    def self.wrapper(id : UInt64?)
+      @@wrapped[id]
+    rescue KeyError
+      nil
+    end
+
+    def self.wrapper(ptr)
+      if id=wrapper_id(ptr.as(LibGObject::Object*))
+        wrapper(id)
+      end
+    end
+
+    def self.wrapper_id(ptr) : UInt64?
+      addr = LibGObject.object_get_data(ptr.as(LibGObject::Object*), GObject::WrappedType::GOBJECT_IS_WRAPPED_TAG).address
+      if addr >= 0
+        addr-1
+      else
+        nil
+      end
+    end
+
+    def self.has_wrapper?(id : Int)
+      @@wrapped.has_key?(id)
+    end
+
+    def self.has_wrapper?(ptr)
+      @@wrapped.has_key?(wrapper_id(ptr.as(LibGObject::Object*)))
+    end    
+
+    def set_data_full(key, data, cb)
+      LibGObject.object_set_data_full(@pointer.as(LibGObject::Object*), key.to_unsafe, data ? data : nil,cb)
+      data
+    end
+
+    def set_wrapped
+      return if !is_a?(GObject::Object)
+      unless has_wrapper?
+        GObject::WrappedType.set_wrapped self
+      end
+    end
+
+    def has_wrapper?
+      return unless is_a?(GObject::Object)
+      GObject::WrappedType.has_wrapper?(@pointer.as(LibGObject::Object*))
+    end
+
+    def wrapper_id
+      if has_wrapper?
+        GObject::WrappedType.wrapper_id(@pointer.as(LibGObject::Object*))
+      end
+    end
+
+    def keep_wrapper
+      GObject::WrappedType.keep_wrapper self
+    end
+
+    def wrapper
+      GObject::WrappedType.wrapper(self)
+    end
+
+    def instantiate
+      raise "foo"
+    end
+  end
+end
+
+lib LibGObject
+  alias DestroyNotify = Void* -> Void
+  fun object_set_data_full = g_object_set_data_full(this : LibGObject::Object*, key : UInt8*, data : Void*, closure : LibGObject::DestroyNotify) : Void
+end
diff --git a/src/g_object/wrapped_type.cr b/src/g_object/wrapped_type.cr
index c5652dc7..029152f7 100644
--- a/src/g_object/wrapped_type.cr
+++ b/src/g_object/wrapped_type.cr
@@ -1,22 +1,54 @@
+require "./wrapped.cr"
+
 module GObject
-  module WrappedType
-    macro def_cast(libtype)
+  module WrappedType  
+    def instantiate()
+    end
+
+    macro init(&b)
+      def instantiate
+        {{b.body}}
+      end
+    end
+  
+    macro def_cast(libtype, type)
       {% if libtype.resolve? %}
-        def self.cast(object) : self
-          new(object.to_unsafe.as({{libtype}}*))
+        def self.cast(object : GObject::WrappedType) : self
+          if object.has_wrapper?
+            if ins = object.wrapper
+              return ins.as(self)
+            end
+          end
+          
+          ins = new(object.void_pointer.as({{libtype}}*)).as(self)
+          ins.set_wrapped
+          ins.instantiate
+          ins
         end
+
+       def self.cast(ptr : Pointer({{libtype}}))
+        if ins=GObject::WrappedType.wrapper(ptr.as(LibGObject::Object*))
+          return ins.as(self)
+        end
+
+        new(ptr).as(self)
+      end    
       {% end %}
     end
 
+    def void_pointer
+      @pointer
+    end 
+
     macro included
       macro inherited
         \{% begin %}
-          def_cast(Lib\{{@type}})
+          def_cast(Lib\{{@type}}, \{{@type}})
         \{% end %}
       end
 
       \{% begin %}
-        def_cast(Lib\{{@type}})
+        def_cast(Lib\{{@type}}, \{{@type}})
       \{% end %}
     end
   end
diff --git a/src/generated/g_object/type_info.cr b/src/generated/g_object/type_info.cr
index fbd8ef77..762f0818 100644
--- a/src/generated/g_object/type_info.cr
+++ b/src/generated/g_object/type_info.cr
@@ -23,7 +23,7 @@ module GObject
       @pointer = pointer.as(Void*)
     end
 
-    def to_unsafe
+    def to_unsafe : LibGObject::TypeInfo*
       @pointer.not_nil!.as(LibGObject::TypeInfo*)
     end
 
@@ -104,7 +104,7 @@ module GObject
     end
 
     def value_table=(value : GObject::TypeValueTable)
-      to_unsafe.as(LibGObject::TypeInfo*).value.value_table = value.to_unsafe.as(LibGObject::TypeValueTable*)
+      to_unsafe.as(LibGObject::TypeInfo*).value.value_table = value.void_pointer.as(LibGObject::TypeValueTable*)
     end
 
   end
diff --git a/src/gtk/gtk.cr b/src/gtk/gtk.cr
index b7fbbd41..bc57e461 100644
--- a/src/gtk/gtk.cr
+++ b/src/gtk/gtk.cr
@@ -73,4 +73,24 @@ module Gtk
       run ARGC_UNSAFE, ARGV_UNSAFE
     end
   end
-end
\ No newline at end of file
+end
+
+class Gtk::Container
+  def children
+    a = [] of Gtk::Widget
+
+    foreach(-> (c : LibGtk::Widget*, d : Void*) {
+      d.as(Array(Gtk::Widget)*).value << Gtk::Widget.cast(c)
+      nil
+    }, pointerof(a).as(Void*))
+
+    a
+  end
+
+  def foreach(&cb : Gtk::Widget -> _)
+    foreach(-> (c : LibGtk::Widget*, d : Void*) {
+      Proc(Gtk::Widget, Nil).new(d, Pointer(Void).null).call Gtk::Widget.cast(c)
+      nil
+    }, cb.pointer)
+  end  
+end