Diagram Elements

The diagram view contains two important elements, “roundtangles” and lines. Class diagrams may also contain annotations (described in the Class Modeling With Xcode Design Tools).

Diagram Tools

The diagram view provides several tools, whose function should be familiar from other drawing packages. You select the tools from the palette in the bottom-left corner of the diagram view, shown in Figure 10-2.

Roll-Up and Expansion

You can display a node and the compartments within it in a variety of ways:

• Rolled up, so that just the name of the class or entity is showing. This gives the most compact representation, with maximum information density in the diagram. (In Figure 10-3 the NSDocument node is rolled up.)

• Compartment titles showing. The titles are Attributes and Relationships in the data model, Properties and Operations in the class model. This gives a compact representation, but with easy access to detail .

• Compartments expanded. All the information in a compartment is visible but at the cost of screen real estate. (In Figure 10-3 the properties compartment of MyDocument is expanded, but the opertations compartment is not.)

To roll up or roll down the node, use Design > Roll Up Compartments or Design > Roll Down Compartments respectively. To hide or expose compartment information, you use the disclosure triangle within a compartment, or Design > Expand Compartments or Design > Collapse Compartments .

Layout

There are a number of options for moving and resizing elements; you can also constrain the way the elements can be moved and resized, and even prevent them from being moved and resized at all. Furthermore, you can zoom into and out of the diagram, and arrange the page layout as you wish.

Moving and Resizing Shapes

You can rearrange elements in a diagram to suit your needs—lines that join elements are updated appropriately. Use the arrow tool to select an element, and then simply drag it. You can move all the elements in the current selection (see Multiple Selection) in the same way.

When you select a shape, “handles” appear around its edges (as shown in Figure 10-4). You can drag the handles to resize the shape as you wish.

You can also automatically resize elements in several ways, using the Design > Diagram > Size menu: Make Same Width and Make Same Height resize the selected elements appropriately; Size to Fit resizes the selected elements so that they fully enclose their contents with minimal padding.

Multiple Selection

You can use multiple selection in the diagram view to move a collection of elements in a flotilla drag, or for roll-up, expand all, and so on. You can make multiple selection in several ways:

• You can select a single element, then hold down the Shift key and click additional elements. Unselected elements are added to the current selection; selected elements are removed from the current selection.

• You can drag the background of the diagram to create a selection rectangle. Elements whose boundaries intersect with this rectangle are selected.

• You can select classes or entities in the browser—the browser selection and diagram selection are kept synchronized.

You can use Edit > Select All to select all elements in the diagram. Note that for items in the Diagram menu, clicking on the background (rather than a drawn element) is the equivalent of selecting all, but may be faster.

Colors and Fonts

The diagram view provides default coloring for various elements . By default, all text is black, and the title bar and outline of drawing elements are colored. In the data model the color is the same for all entities.

You change the background color of the title bar and color of the outline of elements by dropping a color swatch from the Color panel onto the element. You change the other color settings, and the font used for the title, property, and operations text, using the Appearance pane of the Info window (inspector). You can also select multiple elements and change their color and text settings simultaneously, as shown in Figure 10-5.

You can also change the default settings for the entire model using the Appearance pane—see Info Window.

Table View Panes

The left-most pane displays and allows you to edit information about the classes or entities that are in the model. The middle pane displays and allows you to edit information about the properties of the currently selected class or entity. If you make a multiple selection in the class/entity table, the properties table shows the union of all properties of the selection.

As with most table views, you can rearrange and re-sort the columns. You rearrange the columns simply by dragging a header cell; you can change the sort order by clicking in header cells.

You can choose which columns to see by Control clicking table header cells to display a pop-up list that you can use to toggle the display of columns (see Figure 10-7). If you have a multiple selection, Show All Columns means that only the set of columns common to all members of the selection may be displayed, otherwise you get a specific set (dependent upon what you have selected).

You can also choose which properties are shown by clicking the “v” button to the left of the horizontal scroll bar in the property table. This again displays a pop-up list that you can use to toggle the visibility of properties and operations, as shown in Figure 10-8.

Finally, you can display the class/entity list as a flat list or as an inheritance hierarchy. Click the “v” button to the left of the horizontal scroll bar to choose the view option you want as shown in Figure 10-9.

Detail Pane

The detail pane displays detailed information about whatever was last selected in either the entity/class or the property table. If you make a multiple selection, the editor shows the best representation it can of the union of the selected items. If you’re using the data modeling tool, this makes it easy to apply changes to a number of entities or properties simultaneously.

Model Files

The usual way you create a new model file is with the File > New File command and the New File Assistant, shown in Figure 10-11.

For class models, you can also create a quick model from the currently selected items using the Design > Class Model > Quick Model command (see Creating a Quick Model).

Models are considered integral to the project , so you should typically add new class and data models to the project . The exceptions are quick models. Since they are initially considered temporary, you do not have to add them to the project immediately. If you decide to save a quick model, you can add it to the project at a later time. A data model, on the other hand, is a runtime resource (it is compiled, and deployed as part of application), and you should add new data models not only to the project, but also to the relevant target.

You might find it useful to create several different class models in your project. Each model may present subsets of the data in different ways. Each gives a its own perspective on the project, so may be useful for different situations.

Navigation

You can use the browser and diagram views in conjunction for navigation—the selection in the two views is kept synchronized, so if you make a selection in the browser, the same item is selected in the diagram, and vice-versa.

If you want to see a large model in the diagram view, you can maximize the viewable area of a diagram in the main project window by hiding the toolbar, the navigation bar, the status bar, the Favorites bar, and the browser.

If you have a large class diagram, there are two strategies you can use to aid navigation. First, you can type to select classes or entities. As you type characters, the alphabetically “topmost” class or entity whose name has the prefix you typed is selected. Second, you can use the pop-up menu at the top of the document pane. The pop-up shows a list of elements . When you select an item from the pop-up menu (see Figure 10-12), the corresponding element is selected in the diagram and brought into view. This feature may be particularly useful if the browser is hidden.

The browser view, however, is useful when you have a large class diagram with all compartments rolled up, and you want to see more details about a given class, but don’t want to make the diagram bigger. The browser also shows more information than is available in the diagram (parameters, return types and so on).

Contextual Menus

Most menu-based commands are also available from contextual menus associated with the relevant user interface element. You can Control-click a node for immediate access to operations that apply to it or its context, for example to expand compartments, or navigate to documentation. You can Control-click the diagram background to perform operations related both to the visual representation and (in the data model) to the model itself. For example, you can hide grid lines, zoom, set the alignment of drawing elements, and add entities.