Lập trình Wrox Professional Xcode 3 cho Mac OS part 16 pptx

118 ❘ CHAPTER 6 EDITING TEXT Undoing a Cut or Copy command does not restore the previous contents of the system ’ s clipboard. It only restores the state of the editor pane prior to the Cut command. The Redo command performs the complement of the Undo command. It takes the most recent action moved to the redo list, performs it again, and adds it to the undo history. Together, the Undo and Redo commands are like a time machine, allowing you to step forward and backward through the history of the fi le ’ s changes until you fi nd the state of the fi le you want. Any new change made to a fi le erases the redo list. If you go back in time and make a different choice, you can no longer visit the future that contained the original choice. The Revert to Saved command empties both the undo and redo information for a fi le. The Save command does not alter the undo or redo information for a fi le. This means it is possible to undo changes made to a fi le after it has been saved. Whenever you try to undo the last action that occurred before a fi le was saved, Xcode presents a dialog box like the one shown in Figure 6 - 25. FIGURE 6-25 Some developers fi nd this dialog box annoying. Chapter 19 explains how to set the XCShowUndoPastSaveWarning advanced setting to disable that warning. SHELL SCRIPTS If you ’ ve been around the Macintosh platform long enough to remember MPW (the Macintosh Programmer ’ s Workshop), you may be missing one of its more intriguing features. Every text window in MPW was a “ live ” worksheet, capable of executing any MPW command. In fact, MPW made no real distinction between a text document and a shell window. This made for some interesting possibilities. c06.indd 118c06.indd 118 1/22/10 12:20:37 PM1/22/10 12:20:37 PM Download at getcoolebook.com Xcode resurrects this ability, in a fashion, with the hidden Execute Script command. This command is normally bound to the Control + R key combination. It doesn ’ t appear in any of the menus. Select any text and press Control + R. The selected text is executed in your default shell (bash, by default). The output of those commands is inserted into your text fi le immediately after the selected script, as shown on the right in Figure 6 - 26. FIGURE 6-26 The current directory is always set to the active project folder prior to execution, so you can refer to project fi les using project folder – relative paths. A new instance of the shell is used for each invocation, so aliases and shell variables are not persistent. Note that the shell ’ s stdin is set to /dev/ null , making it impossible to use commands that prompt for user input, such as sudo . SPELL CHECKING Programmers are notoriously bad spellers. Thanks to the Cocoa underpinnings of Xcode, the editor inherits the standard Mac OS X spelling checker. The spelling checker is great for correcting comments and documentation, thus avoiding the scorn and ridicule of the documentation department that is inevitably populated with English majors and spelling bee champions. The spelling checker is essentially useless for code. Avoid adding program symbols or language keywords to your user dictionary. Your login account has only one user dictionary, and fi lling it with programming symbols defeats its usefulness in other applications. Interactive Checking Start the interactive spelling checker with the Edit ➪ Spelling ➪ Show Spelling & Grammar (Shift + Command + :) command. This opens the Spelling and Grammar palette (see Figure 6 - 27). Spell Checking ❘ 119 c06.indd 119c06.indd 119 1/22/10 12:20:46 PM1/22/10 12:20:46 PM Download at getcoolebook.com 120 ❘ CHAPTER 6 EDITING TEXT Checking starts at the text cursor or the beginning of the current selection. Checking is not limited to the text selection; it just starts there. The next word that the spelling checker suspects is misspelled is highlighted in the text and displayed in the entry fi eld of the palette. Above the suspect word is a list of suggested corrections. The Ignore button adds the suspect word to the temporary ignore list. The spelling checker ignores this word, and assumes that it is spelled correctly, until the next editor session. Use this to teach the spelling checker temporarily about correctly spelled words, without permanently adding them to the dictionary. The Find Next button skips this word and goes looking for the next suspicious word. The spelling checker still considers the word to be misspelled. You can immediately replace a word with a suggestion from the Guess list by selecting the suggestion and clicking the Change button, or by double - clicking a suggestion in the list. You can replace the word with any arbitrary text by editing the contents of the text fi eld before clicking the Change button. If the spelling checker cannot guess the correct spelling of the word, you can help it by editing the suspect word and telling it to guess again using the Guess button. For example, the spelling checker cannot guess that you mean “ exhausted ” if you ’ ve actually typed “ eghosted. ” Replacing the “ g ” with an “ x ” and clicking the Guess button, as shown in Figure 6 - 28, gets the word close enough for the spelling checker to fi nd the correct word. FIGURE 6-27 c06.indd 120c06.indd 120 1/22/10 12:20:46 PM1/22/10 12:20:46 PM Download at getcoolebook.com The pop - up at the bottom of the palette lets you choose a different language. The Learn and Ignore buttons take the word currently in the entry fi eld and either add or remove it from your user dictionary. To remove a word you previously added, you have to type or paste it into the fi eld before clicking the Ignore button. Your user dictionary is shared by all applications that use the Spelling Checker interface, so add to it wisely and sparingly. Checking One Word You can invoke the spelling checker without bringing up the spelling checker palette with the Edit ➪ Spelling ➪ Check Spelling (Command + ;) command. This command starts at the current location in the fi le and fi nds the next suspect word, which it highlights. That ’ s it. Edit the word in the editor pane or use the command again to fi nd the next suspect word. This is probably the most useful spell checking command for programmers. After writing a long comment, position the cursor at the beginning of the comment and press Command + ;. The spelling checker will skip to the fi rst suspect word in the comment. Once you ’ ve corrected all of the English words in the comment, simply go back to writing code. Checking While Typing The Spelling menu has an option to Check Spelling as You Type. If selected, words that you just typed or edited are spell checked and highlighted automatically. Note that this does not spell check the entire document, or text that you paste or drag. It only checks the word that your cursor was just in or adjacent to. The word that the cursor is currently in or adjacent to is never highlighted (because it is assumed that you are in the process of changing it). You may fi nd this feature useless and annoying when you ’ re editing source code, because practically every “ word ” in your program is going to be tagged as misspelled. However, if you are writing a large amount of documentation in Xcode, you might fi nd it helpful to turn it on temporarily. FIGURE 6-28 Spell Checking ❘ 121 c06.indd 121c06.indd 121 1/22/10 12:20:47 PM1/22/10 12:20:47 PM Download at getcoolebook.com 122 ❘ CHAPTER 6 EDITING TEXT FILE ENCODING Chapter 5 showed you how to change the character and line encoding for one or more fi les using an Info window. You can alter those same settings for the fi le being edited using the View ➪ Text ➪ Line Ending and View ➪ Text ➪ File Encoding menus. Changing these settings does not, immediately, alter the actual fi le. The encodings are used to interpret the bytes in the fi le and turn those codes into Unicode characters for editing. This translation uses the encoding set for the fi le when it is read. Conversely, when the fi le is later saved, the Unicode characters in the editor are translated back into bytes using the encoding that is set then. Problems can arise when you change from one character encoding to another. Some characters cannot be represented in certain encodings or you may have the wrong characters in the editor because the encoding was mismatched when the fi le was read. For instance, the registered trademark symbol ( ® ) appears in the Unicode, Mac OS Roman, and Windows Latin 1 character sets, but the binary code used to represent it in a text fi le is different for all three. If the fi le was written using Windows Latin 1 encoding and you read the fi le into the editor using Mac OS Roman encoding, the editor displays some other symbol because the value in the fi le is not the Mac OS Roman value for the registered trademark symbol. When you change the encoding for a fi le, Xcode asks if it should convert or reinterpret the characters in the fi le, as shown in Figure 6 - 29. The Convert button actually does very little beyond remembering the new encoding for the fi le. The characters are already in their universal form in memory. The “ conversion ” doesn ’ t actually occur until you save the fi le. The bytes in the fi le were read using the old encoding, and will eventually be written using the new encoding. Use this option if the characters in the fi le are correct and you simply want to save the fi le using a different encoding. The one thing the Convert button does do is check that all of the characters in the fi le can be written using the new encoding. Xcode does not allow characters in an editor pane that cannot be encoded when it is saved. If the document contains characters that are illegal in the new encoding, the conversion is not allowed. Use the Reinterpret button when the encoding is incorrect and the editor has misinterpreted the bytes in the fi le. If a fi le containing the registered trademark symbol is encoded using Windows Latin 1, and read using Mac OS Roman, the character that appears in the fi le is “ Æ. ” To correct this, change the encoding to Western (Windows Latin 1) and click the Reinterpret button. The contents of the fi le are read again, this time using the Windows Latin 1 encoding, and the ® symbol appears instead. To save this fi le using Mac OS Roman encoding, change the encoding again — this time using the Convert button. The Reinterpret button must re - read the bytes in the actual fi le. The binary encoding of characters is not maintained in memory — only the Unicode characters are. If changes have been made to a fi le, the Reinterpret button warns you that all unsaved changes will be lost when the fi le is FIGURE 6-29 c06.indd 122c06.indd 122 1/22/10 12:20:50 PM1/22/10 12:20:50 PM Download at getcoolebook.com reinterpreted, as shown in Figure 6 - 30. You can choose to discard all unsaved changes or cancel. To preserve and reinterpret the fi le including all of the changes that you ’ ve made, cancel the reinterpretation, save the fi le using the old encoding, and change the encoding again. As mentioned earlier, Xcode won ’ t allow you to convert a fi le if the resulting document would have characters that cannot be encoded. Likewise, the editor won ’ t let you insert a character into a document if the fi le ’ s encoding won ’ t support it. If you try, you get a warning like the one in Figure 6 - 31. FIGURE 6-30 FIGURE 6-31 You have the choice of converting your document to Unicode (really Unicode - 16) or Unicode - 8. Unicode - 16 is the “ raw ” Unicode encoding used internally by the editor. Unicode - 16 writes or stores each character as a 16 - bit integer word. Most editors, compilers, and other ASCII - oriented programs are not compatible with Unicode - 16. Unicode - 8 writes the common ASCII (0 – 127) characters as single bytes and encodes higher - value Unicode characters using a complex system of escape values. Unicode - 8 is compact, compatible with many applications, and backwards - compatible with plain ASCII text. If given this choice, convert your document to Unicode - 8. If you don ’ t want to use Unicode - 8 or Unicode - 16, cancel the insertion. Convert the fi le to an encoding that supports the characters you are trying to insert, and insert them again. LOCALIZING FILES One of the hallmarks of the Macintosh is the ability of programs to transform themselves to accommodate the language, currency, and time conventions of different countries and populations. This is generically referred to as localization. Xcode supports localization of individual project fi les. It does this by maintaining multiple copies of the fi le, one for each locale. Your locale — the locale that your Xcode development system is currently set to — is called the development region . You should always start by creating the version of a fi le for your development region. When you localize a fi le, the original fi le becomes the version for the development region. You can then create variations of the fi le for other regions. Localizing Files ❘ 123 c06.indd 123c06.indd 123 1/22/10 12:20:51 PM1/22/10 12:20:51 PM Download at getcoolebook.com 124 ❘ CHAPTER 6 EDITING TEXT Normally, you only localize resource fi les like string lists, images, and NIB documents. Localization requires runtime support, and is usually done for fi les that are copied into the deployment bundle. The bundle is organized so that all versions are copied into the bundle and the appropriately localized version of the fi le is loaded based on the locale of the current user. Though it is possible to localize something like a source fi le, only the development region ’ s version will be compiled. Creating Localized Versions of a File To prepare a fi le for localization, open the Info window for the fi le ’ s item and click the Make File Localizable button. The fi le ’ s source item is turned into a group and the existing fi le becomes the localized version for the development region. In the project structure group, the source item becomes a kind of source group. The top - level item acts as a proxy for the development region ’ s version of the fi le, equivalent to the original fi le; that is, opening the item opens the localization for the development region. To open or change settings for an individual locale, expand the group and deal with each version separately. After you initially localize the fi le, you can add more localizations by opening an Info window for either the item group, or any specifi c localization, and clicking the Add Localization button. Enter the name of the localization, or choose one from the pop - up menu, as shown in Figure 6 - 32. A new fi le is created by duplicating the current fi le. The new fi le becomes the localized version for that region. In the project folder, Xcode creates an .lproj subfolder for each localization. All of the fi les localized for English are in the English.lproj subfolder, all the fi les localized for French are in the French.lproj subfolder, and so forth. When the fi le is fi rst localized, a localization folder for the development region is created in the same location, and the fi le is moved into the .lproj subfolder. The Multiglot project, shown in Figure 6 - 33, shows the organization of the project and project folder after the MainMenu.nib and InfoPlist.strings fi les have been localized for English, French, and Spanish. FIGURE 6-32 c06.indd 124c06.indd 124 1/22/10 12:20:56 PM1/22/10 12:20:56 PM Download at getcoolebook.com Removing Some or All Localizations To remove a single localization of a fi le, select the specifi c localization within the fi le ’ s group and delete it like you would any other source item. To remove all localizations of a fi le, open the Info window for the localized group or any specifi c localization. Click the Remove All Localizations button. The localization for the development region is moved from the .lproj subfolder back to its original location. The localized group in the project is replaced with a simple source fi le reference again. Any additional localized versions of the fi le are left in their respective .lproj folders, but are no longer referred to in the project. If you later localize the fi le again, Xcode will not automatically pick up the other localized versions. However, if you add a localization for a region that already has a fi le in its .lproj subfolder, the fi le is not replaced and it becomes the localization for that region. PRINTING Rudimentary printing of editor panes is provided through the File ➪ Print (Command + P) command. The Print command prints the contents of the editor pane, using the editor ’ s font. The gutter, page guide, and other annotations are not printed. Lines wider than the page are always wrapped to the next line; the Wrap Lines setting of the editor pane is ignored. The Use Colors When Printing option in the Font & Colors tab of the Xcode Preferences controls whether editor and syntax coloring is applied to the printout. The text is printed at 72 dpi, which means that it will probably be unacceptably large. Use the scaling feature of the page setup to reduce the size of the text. A scale between 50% and 75% makes for a very readable and compact listing. For an even more compact listing, set the scaling between 80% and 100% and select a two - up page layout. FIGURE 6-33 Printing ❘ 125 c06.indd 125c06.indd 125 1/22/10 12:20:57 PM1/22/10 12:20:57 PM Download at getcoolebook.com 126 ❘ CHAPTER 6 EDITING TEXT SERVICES Xcode, like all well - written Cocoa applications, has access to services. Services are small functions provided by other applications that can be applied to the current selection within another application. To open the URL in the source fi le shown in Figure 6 - 34, simply select it and choose the Open URL command from the Services menu. What services you have in your Services menu depends entirely on what applications and plug - ins you have installed. SUMMARY As you can see, Xcode ’ s editor provides a lot of features designed to make your editing sessions fl uid and productive. Learning to use the various navigation controls will make moving around within a fi le, and between fi les, quick and effi cient. Though the editor provides many useful features for editing and formatting your code, there ’ s a lot more that it can do for you. The next chapter describes the many syntax - aware features of the editor. FIGURE 6-34 c06.indd 126c06.indd 126 1/22/10 12:20:58 PM1/22/10 12:20:58 PM Download at getcoolebook.com . like the one in Figure 6 - 31 . FIGURE 6 -30 FIGURE 6 -31 You have the choice of converting your document to Unicode (really Unicode - 16) or Unicode - 8. Unicode - 16 is the “ raw ” Unicode encoding. shell window. This made for some interesting possibilities. c06.indd 118c06.indd 118 1/22/10 12:20 :37 PM1/22/10 12:20 :37 PM Download at getcoolebook.com Xcode resurrects this ability, in a fashion,. and you read the fi le into the editor using Mac OS Roman encoding, the editor displays some other symbol because the value in the fi le is not the Mac OS Roman value for the registered trademark