Lập trình Wrox Professional Xcode 3 cho Mac OS part 46 docx

346 ❘ CHAPTER 16 TARGETS Target Product Most targets produce a product. The kind of product produced is determined by the type of the target. Application targets produce applications, library targets produce libraries, command - line targets produce UNIX executables, and so on. A special type of target, called an aggregate target, doesn ’ t produce anything itself. It exists solely to group other targets so they can be treated as a single target. In other words, it ’ s a target that “ produces ” other targets. TARGET TYPES It ’ s diffi cult to classify target types in Xcode neatly, because the types form a kind of spectrum. However, the spectrum of target types can be roughly divided between the native and non - native targets. Native targets are at one extreme of the spectrum. They are sophisticated, are tightly integrated into Xcode, are highly confi gurable, have a fl exible number of build phases, and produce complex products (like frameworks). At the other extreme is the non - native external target. An external target simply launches some external process with the understanding that said process will do whatever is necessary to build the target. Xcode doesn ’ t know what an external process will do, what fi les it depends on, or even if it produces anything. An external target has no build phases and is not confi gurable (from within Xcode). In between these two extremes are target types such as aggregate targets and the legacy Jam - based targets. The sophistication of these target types varies. They may have some of the same parts as native targets but are usually simpler and are not as tightly integrated into Xcode. FIGURE 16 - 4 c16.indd 346c16.indd 346 1/21/10 3:55:56 PM1/21/10 3:55:56 PM Download at getcoolebook.com The type of a target is displayed in the General tab of the target ’ s Info window. You cannot change the type of a target. If you fi nd you are using the wrong target type, you must delete the target and create a new target of the correct type. Native Targets The native target types in Xcode are Application, Command - Line Tool, Dynamic Library, Static Library, Framework, Bundle, Kernel Extension, and IOKit Kernel Extension. Native targets are easily identifi ed by their colorful and emotive target icons. Application targets have a small application icon, Command - Line Tool targets are represented by a little terminal screen, Framework targets have a toolbox icon, and the remaining targets appear as plug - ins. Native targets usually have a full complement of parts (build phases, settings, rules, and dependencies). Native targets that include an Info.plist fi le in their product also include a set of properties. See the “ Properties ” section, later in this chapter, for more details. External Targets An external target defi nes a build target that is produced by some external process. This was designed to permit Xcode to integrate with existing workfl ows based on build tools like Make or Ant. The target is little more than a placeholder. It specifi es the tool that will perform the build and the arguments that are passed to it, as shown in Figure 16 - 5. Xcode has no knowledge of what fi les the process requires, what it does, or what it will produce. You cannot add project fi les or build phases to an external target. The section “ Java and Other Jam - Based Targets ” has more information. FIGURE 16 - 5 Target Types ❘ 347 c16.indd 347c16.indd 347 1/21/10 3:55:56 PM1/21/10 3:55:56 PM Download at getcoolebook.com 348 ❘ CHAPTER 16 TARGETS Aggregate Targets Aggregate targets, as the name implies, group several targets together using dependencies. An aggregate target that depends on several different targets can be used to build all of those targets as a unit. Suppose you have developed a suite of BSD command - line tools, each produced by a separate target. To build all of these tools at once, you would create an aggregate target, say it ’ s named “ Tools, ” that depends on all of the Command - Line Tool targets. Now whenever you want to build all of the tools, you simply build the one Tools target. Likewise, you might have applications or other projects that depend on having all of those tools built. Making those targets dependent on the single Tools target is much easier to maintain than adding each tool target to every target that depends on them. Aggregate targets can also be used for utilitarian purposes. Aggregate targets don ’ t produce a product, but they can still be made to do useful work by adding Copy Files or Shell Script build phases. These build phases are executed whenever the target is built, regardless of whether it has any dependencies. See the section “ Build Phases ” for more details about adding build phases to a target. Java and Other Jam - Based Targets Xcode still includes support for the legacy Jam build system, which it inherits from its predecessor, Project Builder. A Jam - based target is a non - native target; the target ’ s build logic is external to Xcode, and the target ’ s confi guration isn ’ t integrated with the rest of Xcode. Jam - based targets are used to implement the external and aggregate target types, and to support legacy targets that were created in Project Builder or obsolete versions of Xcode. Using Jam - Based Targets All Jam - based, non - native targets (as well as the aggregate targets) appear as a red bull ’ s - eye in the Targets smart group. Editing the details of some Jam - based targets is different from editing native targets (you confi gure native targets using the different panes in the target ’ s Info window). All Jam - based targets are confi gured using a target editing window, like the one shown in Figure 16 - 5. See the “ Jam - Based Target Editor ” section later in this chapter for the details. Upgrading Jam - Based Targets Except for the external and aggregate targets, you ’ ll probably want to upgrade any other Jam - based targets to native targets whenever possible. Convert your Jam - based targets into a native target using either the Project ➪ Upgrade to Native Target or the Project ➪ Update All Targets in Project to Native command. These commands are enabled whenever Xcode detects legacy targets originally created with Project Builder or an old version of Xcode. These commands run a conversion process on either the selected Jam - based target or all non - native targets in the project, respectively. Not all Jam - based targets can be converted to native targets. If the conversion is unsuccessful, a report explaining why is produced. If successful, a native target with the same name plus the suffi x “ (Upgraded) ” is created and added to the project. Ensure that the new target functions correctly before deleting the original target. The conversion process does not create new target dependencies, so any targets that depended on the original target have to be edited. The conversion also results in a report, an example of which is shown in Figure 16 - 6. In addition to making a new target, the conversion process may duplicate project fi les. The example in Figure 16 - 6 shows that a duplicate of the Info - StockMarketTicker.plist fi le was made and was named c16.indd 348c16.indd 348 1/21/10 3:55:56 PM1/21/10 3:55:56 PM Download at getcoolebook.com FIGURE 16 - 6 FIGURE 16 - 7 Info - StockMarketTicker__Upgraded_.plist . Delete the original .plist fi le when you delete the original target. You may also want to rename the new .plist fi le, which requires editing the new target ’ s settings to match. Creating a Target ❘ 349 CREATING A TARGET Creating a target is much like adding a new fi le to your project. Choose the Project ➪ New Target command. Alternatively, Right/Control+click the Targets group and choose the Add ➪ New Target command. Either method presents the New Target assistant, shown in Figure 16 - 7. c16.indd 349c16.indd 349 1/21/10 3:55:57 PM1/21/10 3:55:57 PM Download at getcoolebook.com 350 ❘ CHAPTER 16 TARGETS Choose a target template from the list. You ’ ll immediately notice that there are far more templates than target types. Many of the templates produce targets of the same type, but are preconfi gured for different purposes. For example, the Aggregate, Copy Files Target, and Shell Script Target templates all create an aggregate target with no build phases, one Copy Files build phase, or one Run Script build phase, respectively. Because build phases can be easily added or removed, the differences among these templates are trivial. Choose a target template that is as close as possible to the type of product you want to produce. What is of utmost importance is to create a target of the correct type, because you cannot change the type of the target later. If you end up with a target of the wrong type, your only option is to delete the target and start over. The rest is just details. After you ’ ve selected the target template, click the Next button. The assistant presents you with a dialog box to enter a name for the target and select the project you want it added to, as shown in Figure 16 - 8. The product produced by the target initially has the same name as the target. You can alter both the target name and product name later, but to avoid confusion, I suggest keeping them the same whenever practical. If you have more than one project open, select the project that will receive the new target from the Add to Project menu. Click the Finish button. FIGURE 16 - 8 Some templates will also add one or more support fi les to your project. For example, almost any target the produces a bundle (application, framework, plug - in, unit test, and so on) will also need a Info.plist fi le to describe its contents. Adding a new bundle target automatically adds a new Info.plist fi le to your project, typically with a fi lename that mimics the name of the target. Target Template Groups Target templates are organized into groups to make them easier to locate. Start by choosing the group that most closely describes the type of development you are doing (Cocoa, Cocoa Touch, BSD), and then choose your template. Be careful of similarly named templates. The Application template in the Cocoa group produces a signifi cantly different product than the Application template in the Cocoa Touch group. c16.indd 350c16.indd 350 1/21/10 3:55:57 PM1/21/10 3:55:57 PM Download at getcoolebook.com Cocoa Touch Templates Templates in the Cocoa Touch group create targets suitable for producing iPhone applications, static libraries, and unit tests. These are similar to the targets in the Cocoa group, but have different compiler settings and link to different frameworks. TEMPLATE DESCRIPTION Application A native iPhone or iPod Touch application target. The template adds an Info.plist fi le to your project. Static Library A native Static Library target that produces a static library fi le. Unit Test Bundle A unit test bundle, linked to the Foundation framework. Also adds an Info .plist fi le to your project. See Chapter 20 for more information about unit testing. Cocoa Templates Use these targets, listed in the following table, to produce Mac OS X applications, libraries, and shell tools. TEMPLATE DESCRIPTION Application A native Application target that produces an application bundle linked to the Cocoa framework. This template adds an Info .plist fi le to your project. Dynamic Library A native Dynamic Library target that produces a .dylib library fi le, itself linked to the Cocoa framework. Framework A native Framework bundle target. This template adds an Info .plist fi le to your project. Loadable Bundle A native Bundle target that produces a generic bundle linked to the Cocoa framework. This template adds an Info.plist fi le to your project. Shell Tool A native Command - Line target that produces a BSD executable binary. Static Library A native Static Library target that produces a static library fi le, itself linked to the Cocoa framework. Unit Test Bundle A native Bundle target confi gured to produce a unit test written using the Cocoa framework. See Chapter 20 for more information about unit testing. This template adds an Info.plist fi le to your project. Creating a Target ❘ 351 c16.indd 351c16.indd 351 1/21/10 3:55:58 PM1/21/10 3:55:58 PM Download at getcoolebook.com 352 ❘ CHAPTER 16 TARGETS The Loadable Bundle is the catch - all template for creating virtually any kind of bundle. If you can ’ t fi nd a template for the particular type of bundle (application, plug - in, and so on) that you ’ re trying to create, start with the Loadable Bundle template. Application Plug - In Templates The only template currently in this group is the Automator Action template: TEMPLATE DESCRIPTION Automator Action A native Bundle target that includes a Compile AppleScript Files phase, suitable for producing Automator Action bundles. This template adds an Info.plist fi le to your project. BSD Templates The BSD templates, listed in the following table, create targets that produce fl at BSD executable or library fi les. TEMPLATE DESCRIPTION Dynamic Library A native Dynamic Library target that produces a .dylib library fi le. Object File A native Object File target that compiles a single module using the BSD APIs. Shell Tool A native Command - Line target that produces a BSD executable binary. Static Library A native Static Library target that produces a static library fi le. System Plug - Ins Templates The two templates, listed in the following table, create the specialized targets used to produce kernel extension bundles. TEMPLATE DESCRIPTION Generic Kernel Extension A Kernel Extension target that produces a kernel extension bundle. IOKit Driver An IOKit Kernel Extension target that produces a kernel extension bundle. Other Templates The targets listed in the following table create empty or placeholder targets. None of these targets produces a product, although the process launched by an external target is expected to build something. c16.indd 352c16.indd 352 1/21/10 3:55:58 PM1/21/10 3:55:58 PM Download at getcoolebook.com TARGET DESCRIPTION Aggregate An empty Aggregate target. Copy Files An Aggregate target with a single Copy Files build phase. External A Jam - based External target. External targets run some external process (like make) to build the target. They cannot have build phases. Shell Script An Aggregate target with a single Run Script build phase. Legacy If you upgraded an earlier version of Xcode, your installation may contain additional target templates that have since been removed from the Xcode Developer Tools. These might include Java Applet, Carbon, and other deprecated targets. For the most part, Xcode still supports these legacy target templates, but may not in the future. Duplicating Targets You can also create a new target by duplicating an existing one. This is especially useful if you need a new target that is very similar to one that already exists. Select the target in the Targets smart group. In the Right/Control+click contextual menu choose the Duplicate command. A duplicate of the target is created with the suffi x “ copy ” appended to the target ’ s name. Note that the new target is an exact duplicate except, of course, for its name. If the original target produced a product, the new target will produce the same product. Assuming you want the targets to build separate products, remember to edit the settings of the target so the two products don ’ t overwrite one another. Deleting Targets To delete a target, select the target in the Targets smart group. Press the Delete key or choose Delete from the Right/Control+click contextual menu. Xcode presents a warning that removing a target will also remove the reference to it in any targets that depend on it. Click the Delete button to acknowledge the warning and delete the target. BUILD PHASES Build phases defi ne the steps that must occur in order to build a target. Build phases tend to paint with a broad brush. Targets typically have one Compile Sources build phase that compiles all of the source fi les for that target, even if that includes source fi les from many different languages. Consequently, targets rarely have more than three or four build phases. Use the disclosure triangle next to the target ’ s name in the Targets smart group to reveal the build phases for the target, as shown in Figure 16 - 9. The list of fi les on which a build phase will operate, or depends, is referred to as the phase ’ s input fi les. Selecting a build phase lists the input Build Phases ❘ 353 c16.indd 353c16.indd 353 1/21/10 3:55:58 PM1/21/10 3:55:58 PM Download at getcoolebook.com . some of the same parts as native targets but are usually simpler and are not as tightly integrated into Xcode. FIGURE 16 - 4 c16.indd 34 6c16.indd 34 6 1/21/10 3: 55:56 PM1/21/10 3: 55:56 PM Download. input fi les. Selecting a build phase lists the input Build Phases ❘ 35 3 c16.indd 35 3c16.indd 35 3 1/21/10 3: 55:58 PM1/21/10 3: 55:58 PM Download at getcoolebook.com . assistant, shown in Figure 16 - 7. c16.indd 34 9c16.indd 34 9 1/21/10 3: 55:57 PM1/21/10 3: 55:57 PM Download at getcoolebook.com 35 0 ❘ CHAPTER 16 TARGETS Choose a target template from the list. You