Split the Combobox Example Model into Three Models

This simplifies lifetime handling for these comboboxes.

BUG=897377

Change-Id: I19e8ed25f8e6b17012669ad7e810d33aa28d8ec8
Reviewed-on: https://chromium-review.googlesource.com/c/1295589Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602174}

ui/views/examples/combobox_example.cc

@@ -4,6 +4,8 @@
 
 #include "ui/views/examples/combobox_example.h"
 
+#include <memory>
+
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/gfx/geometry/insets.h"
@@ -13,44 +15,43 @@
 namespace views {
 namespace examples {
 
-ComboboxModelExample::ComboboxModelExample() {
-}
+namespace {
 
-ComboboxModelExample::~ComboboxModelExample() {
-}
+// A combobox model implementation that generates a list of "Item <index>".
+class ComboboxModelExample : public ui::ComboboxModel {
+ public:
+  ComboboxModelExample() = default;
+  ~ComboboxModelExample() override = default;
 
-int ComboboxModelExample::GetItemCount() const {
-  return 10;
-}
+ private:
+  // ui::ComboboxModel:
+  int GetItemCount() const override { return 10; }
+  base::string16 GetItemAt(int index) override {
+    return base::UTF8ToUTF16(base::StringPrintf("%c item", 'A' + index));
+  }
 
-base::string16 ComboboxModelExample::GetItemAt(int index) {
-  return base::UTF8ToUTF16(base::StringPrintf("%c item", 'A' + index));
-}
+  DISALLOW_COPY_AND_ASSIGN(ComboboxModelExample);
+};
+
+}  // namespace
 
 ComboboxExample::ComboboxExample() : ExampleBase("Combo Box") {
 }
 
-ComboboxExample::~ComboboxExample() {
-  // Delete |combobox_| first as it references |combobox_model_|.
-  delete combobox_;
-  delete disabled_combobox_;
-  delete action_combobox_;
-  combobox_ = nullptr;
-  disabled_combobox_ = nullptr;
-  action_combobox_ = nullptr;
-}
+ComboboxExample::~ComboboxExample() = default;
 
 void ComboboxExample::CreateExampleView(View* container) {
-  combobox_ = new Combobox(&combobox_model_);
+  combobox_ = new Combobox(std::make_unique<ComboboxModelExample>());
   combobox_->set_listener(this);
   combobox_->SetSelectedIndex(3);
 
-  disabled_combobox_ = new Combobox(&combobox_model_);
+  disabled_combobox_ = new Combobox(std::make_unique<ComboboxModelExample>());
   disabled_combobox_->set_listener(this);
   disabled_combobox_->SetSelectedIndex(4);
   disabled_combobox_->SetEnabled(false);
 
-  action_combobox_ = new Combobox(&combobox_model_, Combobox::STYLE_ACTION);
+  action_combobox_ = new Combobox(std::make_unique<ComboboxModelExample>(),
+                                  Combobox::STYLE_ACTION);
   action_combobox_->set_listener(this);
   // Note: STYLE_ACTION comboboxes always have the first item selected by
   // default.
@@ -64,11 +65,14 @@ void ComboboxExample::CreateExampleView(View* container) {
 
 void ComboboxExample::OnPerformAction(Combobox* combobox) {
   if (combobox == combobox_) {
-    PrintStatus("Selected: %s", base::UTF16ToUTF8(combobox_model_.GetItemAt(
-        combobox->selected_index())).c_str());
+    PrintStatus("Selected: %s",
+                base::UTF16ToUTF8(
+                    combobox->model()->GetItemAt(combobox->selected_index()))
+                    .c_str());
   } else if (combobox == action_combobox_) {
-    PrintStatus("Action: %s", base::UTF16ToUTF8(combobox_model_.GetItemAt(
-        combobox->selected_index())).c_str());
+    PrintStatus("Action: %s", base::UTF16ToUTF8(combobox->model()->GetItemAt(
+                                                    combobox->selected_index()))
+                                  .c_str());
   } else {
     NOTREACHED() << "Surprising combobox.";
   }

ui/views/examples/combobox_example.h

@@ -13,20 +13,6 @@
 namespace views {
 namespace examples {
 
-// A combobox model implementation that generates a list of "Item <index>".
-class VIEWS_EXAMPLES_EXPORT ComboboxModelExample : public ui::ComboboxModel {
- public:
-  ComboboxModelExample();
-  ~ComboboxModelExample() override;
-
-  // ui::ComboboxModel:
-  int GetItemCount() const override;
-  base::string16 GetItemAt(int index) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ComboboxModelExample);
-};
-
 class VIEWS_EXAMPLES_EXPORT ComboboxExample : public ExampleBase,
                                               public ComboboxListener {
  public:
@@ -40,7 +26,6 @@ class VIEWS_EXAMPLES_EXPORT ComboboxExample : public ExampleBase,
   // ComboboxListener:
   void OnPerformAction(Combobox* combobox) override;
 
-  ComboboxModelExample combobox_model_;
   Combobox* combobox_ = nullptr;
   Combobox* disabled_combobox_ = nullptr;
   Combobox* action_combobox_ = nullptr;