The Object Repository

The Object Repository

Delphi has menu commands you can use to create a new form, a new application, a new data module, a new component, and so on. These commands are located in the File ® New menu and in other pull-down menus. If you simply select File ® New ® Other, Delphi opens the Object Repository. You can use it to create new elements of any kind: forms, applications, data modules, thread objects, libraries, components, automation objects, and more.

The New Items dialog box (shown in Figure 1.12) has several pages, hosting all the new elements you can create, existing forms and projects stored in the Repository, Delphi wizards, and the forms of the current project (for visual form inheritance). The pages and the entries in this tabbed dialog box depend on the specific version of Delphi, so I won't list them here.

Click To expand
Figure 1.12: The first page of the New Items dialog box, generally known as the Object Repository

The Object Repository has a shortcut menu you can use to sort its items in different ways ( by name, by author, by date, or by description) and to show different views ( large icons, small icons, lists, and details). The Details view gives you the description, the author, and the date of the tool—information that is particularly important when you're looking at wizards, projects, or forms that you've added to the Repository.

The simplest way to customize the Object Repository is to add new projects, forms, and data modules as templates. You can also add new pages and arrange the items on some of them (not including the New and "current project" pages). Adding a new template to Delphi's Object Repository is as simple as using an existing template to build an application. When you have a working application you want to use as a starting point for further development of similar programs, you can save the current status to a template, and it will be ready to use later. Simply use the Project ® Add To Repository command, and fill in its dialog box.

Just as you can add new project templates to the Object Repository, you can also add new form templates. Move to the form that you want to add, and select the Add To Repository command from its shortcut menu. Then, indicate the title, description, author, page, and icon in the resulting dialog box. Keep in mind that as you copy a project or form template to the Repository and then copy it back to another directory, you are simply doing a copy-and-paste operation; this isn't much different than copying the files manually.

To further customize the Repository, you can use the Tools ® Repository command. This command opens the Object Repository dialog box, which you can use to move items to different pages, to add new elements, or to delete existing elements. You can even add new pages, rename or delete them, and change their order. An important element of the Object Repository setup is the use of defaults:

  • Use the New Form check box below the list of objects to designate a form as the one to be used when a new form is created (File ® New Form).

  • The Main Form check box indicates which type of form to use when creating the main form of a new application (File ® New Application), if no special New Project is selected.

  • The New Project check box, available when you select a project, marks the default project that Delphi will use when you issue the File ® New Application command.

Only one form and only one project in the Object Repository can have each of these three settings marked with a special symbol placed over its icon. If no project is selected as New Project, Delphi creates a default project based on the form marked as Main Form. If no form is marked as the main form, Delphi creates a default project with an empty form.

When you work on the Object Repository, you work with forms and modules saved in the OBJREPOS subdirectory of the Delphi main directory. At the same time, if you use a form or any other object directly without copying it, then you end up having some of your project files in this directory. It is important to realize how the Repository works, because if you want to modify a project or an object saved in the Repository, the best approach is to operate on the original files without copying data back and forth to the Repository.

Part I: Foundations