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

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

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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

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FIGURE 14-12

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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

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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

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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

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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

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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

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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

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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

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

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FIGURE 14-20

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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

continues

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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)

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