Lập trình Wrox Professional Xcode 3 cho Mac OS part 40 doc

You can add class nodes to the selection by holding down the Shift key while clicking unselected nodes or dragging out a selection rectangle. Nodes can be individually removed from a selection by clicking a selected node while holding down the Shift key. It may be necessary to click the background area or the edge of a node; clicking the node ’ s title or a member may not deselect it. You can also type the fi rst few letters of a class name. When listed alphabetically, the fi rst class that matches the characters typed is selected. Quick - Jump to Source Double - click any class or member in the class browser, and Xcode jumps to its declaration in the source code. In the class diagram, Right/Control+click on a node, as shown in Figure 14 - 12, and choose one of the commands: Go to Declaration Go to Defi nition Go to Documentation These same three commands can be found in the Design ➪ Class Model submenu. If an individual property or operation in the node is selected, Xcode jumps to that specifi c instance variable or method. Otherwise, you are taken to the class ’ s defi nition, implementation, or documentation. If a class or method appears in the API documentation, a small “ book ” icon appears next to its name in the browser. Clicking the book icon jumps to its documentation, and is the same as choosing the Design ➪ Class Model ➪ Go to Documentation command. EDITING A CLASS MODEL “ Editing ” a class diagram is limited to customizing its appearance. As mentioned at the beginning of this chapter, you can ’ t alter the defi nition of a class in a class model. Class modeling is strictly a visualization tool. Any changes you make will be (mostly) cosmetic. That said, you can alter the layout and appearance of the class diagram signifi cantly, which can profoundly infl uence its effectiveness as a programming aid. Moving Nodes The main point of class diagrams is to visually represent the relationship between classes. Creating a pleasing and readable distribution of class nodes is, therefore, paramount to creating a useful class ➤ ➤ ➤ FIGURE 14-12 Editing a Class Model ❘ 297 c14.indd 297c14.indd 297 1/21/10 3:41:57 PM1/21/10 3:41:57 PM Download at getcoolebook.com 298 ❘ CHAPTER 14 CLASS MODELING model. Xcode provides a variety of tools and techniques by which you can reshape a class diagram. The inheritance lines between class nodes are permanent fi xtures and will follow the nodes as you reposition them. In fact, organizing the diagram such that all of the inheritance lines are visible and unambiguous will be your biggest challenge. You can move nodes individually, or in groups, by selecting and dragging them to a new position. You can also use the arrow keys on the keyboard to move selected nodes. A variety of alignment commands are found in the Design ➪ Alignment ➪ Align menu. Most of these are self - explanatory, and apply to the currently selected nodes. You must have at least two nodes selected for the alignment commands to work. These same commands are located in the Alignment submenu of the node ’ s contextual menu in the diagram. Automatic Layout Xcode provides two algorithms for automatically rearranging class nodes: hierarchical and force - directed. Select the set of nodes you want laid out — or select none to rearrange them all — and choose the desired layout command from the Design ➪ Automatic Layout menu. Hierarchical layout, shown in Figure 14 - 13, produces graphs where sister nodes (two nodes that inherit from a common node) are distributed horizontally. For large collections of classes that all descend from the same class (NSObject, for instance), this can create very wide diagrams. FIGURE 14-13 Force - directed layout tends to put progenitor classes in the middle of the diagram, with descendants radiating outward. Imagine that all of the nodes are negatively charged particles that are equally repelled by all other nodes. Imagine that the lines connecting the nodes are elastic bands. Now, pick up the root nodes of the model and let the remaining nodes hang like a mobile. This is, approximately, the effect of force - directed layout. The diagram in Figure 14 - 13 is the same diagram shown in Figure 14 - 12, reorganized using force - directed layout. c14.indd 298c14.indd 298 1/21/10 3:41:58 PM1/21/10 3:41:58 PM Download at getcoolebook.com Hierarchical layout is the most predictable and produces extremely easy - to - see relationships, but it can produce unwieldy results for large collections of classes. Force - directed layout produces compact graphs, but they are often unintuitive. The release notes for Xcode also warn that the algorithm used to generate force - directed layouts is “ unbounded, ” meaning that it can take an indeterminate amount of CPU time to compute the layout of a large and complex diagram. Xcode uses hierarchical automatic layout when a model is fi rst created, and whenever the tracking for the model is changed. Automatic layout uses the current size of each node, and tries to create layouts such that nodes do not overlap. Locked nodes (see the “ Locking Nodes ” section) can interfere with this goal. Resizing Nodes You can resize nodes using the resize “ handles ” that appear on the edges of the node when it is selected. Choose the Design ➪ Diagram ➪ Size ➪ Size to Fit command to resize selected nodes such that their height and width are exactly enough to show their entire names and all exposed members. The height of a node does this automatically whenever the compartments are rolled up, rolled down, expanded, or collapsed. The width, however, is never automatically adjusted. If you want the width to be suffi cient to show all members, have those compartments expanded before using the Size to Fit command. You can also set the height or width of multiple nodes so that they are all identical. Begin by selecting a prototype node. Select additional nodes by holding down the Shift key. The Size ➪ Make Same Width and Size ➪ Make Same Height commands set the width or the height of all selected nodes so that they are identical to the dimension of the prototype node. Locking Nodes Locking a node prevents it from being moved or resized. To lock or unlock a node, or nodes, use the Lock and Unlock commands in the Design ➪ Diagram or the node ’ s contextual menu. Locking is very useful for preserving the layout of a subgroup of nodes, while you add, remove, or rearrange other nodes around them. FIGURE 14-14 Editing a Class Model ❘ 299 c14.indd 299c14.indd 299 1/21/10 3:41:58 PM1/21/10 3:41:58 PM Download at getcoolebook.com 300 ❘ CHAPTER 14 CLASS MODELING Grid and Grid Alignment As an aid to positioning and sizing nodes, Xcode provides an optional grid. The grid is drawn in light gray behind the diagram, as shown in Figure 14 - 15. When you ’ re dragging nodes around, their position will normally “ snap ” to the nearest grid line. To enable or disable grid snap, choose the Design ➪ Diagram ➪ Turn Grid On/Off command in the main menu or simply Right/Control+click on the background of the diagram. Use the Design ➪ Diagram ➪ Hide/Show Grid command to hide and reveal the grid. Grid snap is independent of its visibility. Page Layout A class diagram occupies a series of pages. Like a WYSIWYG word processor or spreadsheet, Xcode extends the graph area in page increments to accommodate the size of the diagram. Drag a node off the edge of the page, and a new page appears. A solid gray line indicates the boundary between pages. If you plan to print a diagram, you can use the page guides to ensure that nodes don ’ t straddle two or more pages. If they are unimportant, the page guides can be hidden using the Design ➪ Diagram ➪ Show/Hide Page Breaks command. The size of a page is controlled using the File ➪ Page Setup command. By default, Xcode sets the page magnifi cation to 80 percent and the orientation to landscape. Smaller magnifi cation values shrink the size of the node, allowing you to fi t more nodes on a page. Consider passing out reading glasses if you reduce the page magnifi cation below 50 percent. Changing the Tracking You can add or remove classes to and from a class model at any time. Click the diagram background, so that no nodes are selected, and then choose the File ➪ Get Info command. This opens the Info window for the class model. Switch to the Tracking tab. In it, you will fi nd the list of source fi les and groups the class model is tracking. To remove fi les or groups, select them in the list and click the - button at the bottom of the window. Changing the tracking may add, remove, or replace existing nodes. This may cause customized diagrams to lose some of their customization. At the very least, any change will perform an automatic hierarchical layout, undoing any hand-arranged node positions. Save your document before changing your document’s tracking — or better yet, take a snapshot or check it into source control fi rst. FIGURE 14-15 c14.indd 300c14.indd 300 1/21/10 3:41:59 PM1/21/10 3:41:59 PM Download at getcoolebook.com To add new sources, click the + button. This presents the sheet shown in Figure 14 - 16. Select the additional sources you want added to the model and click the Add Tracking button. FIGURE 14-16 I n its current incarnation, Xcode occasionally exhibits problems constructing class models. The symptom is missing inheritance between classes, protocols, or categories. If this happens, try removing the subclass and adding it back to the model following the classes and other nodes it inherits from. If that doesn ’ t work, create a new, empty, model. Add classes in batches, starting with the superclasses, in such a way that you never add a class unless all of the superclasses and interfaces or protocols from which it inherits are already in the model. An easy way of accomplishing this is to keep the Class Browser window visible behind the diagram ’ s Info window. That way, you can easily refer to the hierarchical arrangement of classes as you add them to the model. Editing a Class Model ❘ 301 c14.indd 301c14.indd 301 1/21/10 3:42:05 PM1/21/10 3:42:05 PM Download at getcoolebook.com 302 ❘ CHAPTER 14 CLASS MODELING Adding Annotations Beyond altering its appearance, the only real content that can be added to a class diagram is an annotation node. Create annotation nodes by dragging out a rectangle using the Note tool, or by choosing the Design ➪ Class Model ➪ Add Comment command. An annotation node has a page - like, or sticky - note - like, appearance, as shown in Figure 14 - 17. The content of the node is free - formed text. Double - click the node to enter text edit mode. All of the typographical formatting features in the Edit ➪ Format ➪ Font and Edit ➪ Format ➪ Text submenus can be used, which gives you an immense amount of formatting control. Even the text rulers and tab stops work, although they seem a little silly in an area only big enough for a sentence or two. Annotation nodes can be connected to any number of other regular nodes, but not another annotation node. To connect an annotation node to a class node, use the Line tool to drag out a line between the two nodes. To remove a connection or an annotation node, select the line or node and press the Delete key or choose Edit ➪ Delete. Customizing Colors and Fonts You can customize the text color, font, size, and style of nodes in the Appearance tab of the Info window. Choose File ➪ Get Info with one or more nodes selected to alter the appearance of those nodes. With no node selected, the Info window allows you to set the default settings for new nodes; the default settings apply only to new nodes created by adding additional classes to the model. Figure 14 - 18 shows the Appearance tab. The three categories — Name, Property, and Operation — address the three compartments of each node. Changing the color changes the color of the text. Changing the font, by clicking the Set button to the right of each sample, allows you to change the font face, style, and size of the text of each compartment. FIGURE 14-17 FIGURE 14-18 c14.indd 302c14.indd 302 1/21/10 3:42:08 PM1/21/10 3:42:08 PM Download at getcoolebook.com You can change the background color used in the title to distinguish between different types of nodes — in a roundabout way. Drop a color from any color source onto a node to change its background color. Probably the easiest way to get a color source is to choose Edit ➪ Format ➪ Font ➪ Show Colors to display the color picker. Dial a color, and then drag the color sample at the top of the picker into the node. Figure 14 - 19 shows nodes with customized colors. FIGURE 14-19 Hiding Classes and Members One of the primary uses of a class diagram is to maintain a high - level vision of class relationships — but sometimes there can be so many classes, class members, protocols, and categories that its essence is obscured by the details. You can regain some perspective by selectively hiding superfl uous classes and members. You can do this on a per - class basis or automate it using rules. You might want to hide classes or certain members of classes for many reasons: Private or protected members that shouldn ’ t be exposed Internal utility or helper classes Base class methods, like - (NSUInteger)hash , that don ’ t add anything signifi cant to the description of the classes Unrelated or superfl uous classes that happen to be defi ned in the same fi le as important classes Categories that are unrelated or are used to hide private methods ➤ ➤ ➤ ➤ ➤ Editing a Class Model ❘ 303 c14.indd 303c14.indd 303 1/21/10 3:42:09 PM1/21/10 3:42:09 PM Download at getcoolebook.com 304 ❘ CHAPTER 14 CLASS MODELING Selectively hiding classes and class elements lets you pair down the diagram to exactly the detail you want to see. For example, an Objective - C class that can be archived probably implements initWithCoder: and encodeWithCoder: . Having these methods listed in every single class node really doesn ’ t impart any useful information. Why you would want to hide elements also depends a lot on your goals. If you ’ re using a class model as an aide to developing your code, you ’ ll probably want to see all of the private and protected members. If your intent is to provide a class model to other developers as a means of documenting how your classes relate and their public functionality, private and protected variables probably shouldn ’ t be visible. You can individually control the visibility of classes, protocols, categories, and packages. Or, you can create rules to determine which classes are visible automatically. You can also create rules to determine the visibility of properties and operations; those can ’ t be set individually. Start by manually setting the visibility of classes. To set the visibility of one or more classes manually: 1. Select a node or nodes in the diagram, or select one or more classes in the class list. 2. In the details pane of the browser (upper right), set the visibility of the class or classes to: Hide per Filter Always Show Always Hide Choosing Always Show or Always Hide fi xes the visibility of the class in the diagram. Selecting the Hide per Filter option shows, or hides, the class based on the model ’ s classes fi lter. When this option is selected, a line of text below the control indicates the visibility of the class based on the fi lter. There is also a Hidden column available in the class list of the browser. Right/ Control+click the class column titles and reveal the Hidden column in the table. Click the box in the row of each class to selectively hide (checked), show (unchecked), or fi lter it (indeterminate). You can create class, property, and operation fi lters in the General tab of the diagram ’ s Info window. Make sure no nodes are selected, and then choose File ➪ Get Info (Command+I) to open the Info window. At the bottom of the Info window are three fi lter settings, shown in Figure 14 - 20. To enable a fi lter, check the box next to the desired fi lter. If disabled (or the fi lter rule is left empty), the fi lter will not hide any nodes in the diagram. ➤ ➤ ➤ FIGURE 14-20 c14.indd 304c14.indd 304 1/21/10 3:42:10 PM1/21/10 3:42:10 PM Download at getcoolebook.com If you ’ re conversant in Mac OS X ’ s predicate language, you can edit the predicate statement directly in the text fi eld. If you ’ re like me and need some help constructing the condition statement, click the Edit Filter button. Xcode presents a predicate editor, as shown in Figure 14 - 21. FIGURE 14-21 The predicate editor allows you to graphically create arbitrarily complex conditional statements. The predicate editor is described in more detail in Chapter 15, but here ’ s the short version. An expression is built from basic conditionals. A condition consists of three parts: variable, operator, and value. Variables are properties of each node or member in the class model, and the set of variables is fi xed. For properties and operations, the variables are Name, Visibility, Type, and Static. For classes, the variables are Name, Kind, Superclass, Language, and Project Member. These variables are described in the following table: VARIABLE DESCRIPTION Name The class or member ’ s name. Kind The type of the class node in the diagram: Class, Protocol, Interface, or Category. Superclass The name of the class that the class or category extends. Language The language in which the class was defi ned: C++, Java, or Objective - C. Project Member This value will be Yes if the class is defi ned in the project. Editing a Class Model ❘ 305 continues c14.indd 305c14.indd 305 1/21/10 3:42:11 PM1/21/10 3:42:11 PM Download at getcoolebook.com 306 ❘ CHAPTER 14 CLASS MODELING VARIABLE DESCRIPTION Visibility The visibility or scope of the property or operation: Public, Package, Protected, or Private. Type The type of the variable. Static This value will be Yes if the property or operation is a static or class member. To confi gure a conditional, select the variable from the left side and an operation from the middle, and then enter a value or a select a constant on the right side. You can insert a new Boolean operator into the expression by choosing the Add AND or Add OR item in either a variable or Boolean operator menu. Adding a Boolean operator makes the entire subexpression one term in a new Boolean operator clause. Each Boolean operator logically combines the results of two or more subexpressions. You can add or remove subexpressions to or from a Boolean operator using the round plus and minus buttons on the right. To remove a Boolean operator, remove all but one of its subexpressions. You can negate a conditional or Boolean operator by selecting the Add NOT item. This inserts a negation operator, which you can remove again by choosing Remove in its menu. Figures 14 - 22, 14 - 23, and 14 - 24 present a practical example that uses three predicate formulas to fi lter a class diagram. The goal is to hide much of the minutia — simple framework classes, common methods, private instance variables, and so on — that would otherwise clutter the diagram. The Hide Classes rule, shown in Figure 14 - 22, hides the NSObject base class and every immediate subclass of NSObject that is not defi ned in the current project. FIGURE 14-22 (continued) c14.indd 306c14.indd 306 1/21/10 3:42:11 PM1/21/10 3:42:11 PM Download at getcoolebook.com [...]...Summary ❘ 30 7 The Hide Properties rule, shown in Figure 14 - 23, hides all properties that are private or whose name begins with an underscore (_) character The Hide Operations rule, shown in Figure 14 -24, hides the following methods in every class: FIGURE 14- 23 ➤ -dealloc ➤ -compare: ➤ -description ➤ Any method that starts with an underscore character ➤ Any method whose name ends in WithZone:... time objects can be The next chapter combines these two technologies, allowing you to visually design your data model objects Download at getcoolebook.com c14.indd 30 7 1/21/10 3: 42:12 PM Download at getcoolebook.com c14.indd 30 8 1/21/10 3: 42:12 PM . ➤ ➤ ➤ ➤ ➤ FIGURE 14- 23 FIGURE 14-24 Summary ❘ 30 7 c14.indd 30 7c14.indd 30 7 1/21/10 3: 42:12 PM1/21/10 3: 42:12 PM Download at getcoolebook.com c14.indd 30 8c14.indd 30 8 1/21/10 3: 42:12 PM1/21/10 3: 42:12 PM Download. private methods ➤ ➤ ➤ ➤ ➤ Editing a Class Model ❘ 30 3 c14.indd 30 3c14.indd 30 3 1/21/10 3: 42:09 PM1/21/10 3: 42:09 PM Download at getcoolebook.com 30 4 ❘ CHAPTER 14 CLASS MODELING Selectively hiding. the diagram. ➤ ➤ ➤ FIGURE 14-20 c14.indd 30 4c14.indd 30 4 1/21/10 3: 42:10 PM1/21/10 3: 42:10 PM Download at getcoolebook.com If you ’ re conversant in Mac OS X ’ s predicate language, you can edit