NSSpellChecker

Inherits From: NSObject

Conforms To: NSObject (NSObject)

Declared In: AppKit/NSSpellChecker.h

Class Description

The NSSpellChecker class gives any application an interface to the OpenStep spell-checking service. To handle all its spell checking, an application needs only one instance of NSSpellChecker. It provides a panel in which the user can specify decisions about words that are suspect. To check the spelling of a piece of text, the application:

. Includes in its user interface a menu item (or a button or command) by which the user will request spell checking.

. Makes the text available by way of an NSString object.

. Creates an instance of the NSSpellChecker class and sends it a checkSpellingOfString:startingAt: message.

For example, you might use the following statement to create an NSSpellChecker:

range = [[NSSpellChecker sharedSpellChecker] checkSpellingOfString:aString startingAt:0];

The checkSpellingOfString:startingAt: method checks the spelling of the words in the specified string beginning at the specified offset (this example uses 0 to start at the beginning of the string) until it finds a word that is misspelled. Then it returns an NSRange to indicate the location of the misspelled word.

In a graphical application, whenever a misspelled word is found, you'll probably want to highlight the word in the document, using the NSRange that checkSpellingOfString:startingAt: returned to determine the text to highlight. Then you should show the misspelled word in the Spelling panel's misspelled-word field by calling updateSpellingPanelWithMisspelledWord:. If checkSpellingOfString:startingAt: does not find a misspelled word, you should call updateSpellingPanelWithMisspelledWord: with the empty string. This causes the system to beep, letting the user know that the spell check is complete and no misspelled words were found. None of these steps is required, but if you do one, you should do them all.

The object that provides the string being checked should adopt the following protocols:

NSChangeSpelling A message in this protocol (changeSpelling:) is sent down the responder chain when the user presses the Correct button.

NSIgnoreMisspelledWords When the object being checked responds to this protocol, the spell server keeps a list of words that are acceptable in the document and enables the Ignore button in the Spelling panel.

The application may choose to split a document's text into segments and check them separately. This will be necessary when the text has segments in different languages. Spell checking is invoked for one language at a time, so a document that contains portions in three languages will require at least three checks.

Dictionaries and Word Lists

The process of checking spelling makes use of three references:

. A dictionary registered with the system's spell-checking service. When the Spelling panel first appears, by default it shows the dictionary for the user's preferred language. The user may select a different dictionary from the list in the Spelling panel.

. The user's learn list of correctly-spelled words in the current language. The NSSpellChecker updates the list when the user presses the Learn or Forget buttons in the Spelling panel.

. The document's list of words to be ignored while checking it (if the first responder conforms to the NSIgnoreMisspelledWords protocol). The NSSpellChecker updates its copy of this list when the user presses the Ignore button in the Spelling panel.

A word is considered to be misspelled if none of these three accepts it.

Matching a List of Ignored Words with the Document It Belongs To

The NSString being checked isn't the same as the document. In the course of processing a document, an application might run several checks based on different parts or different versions of the text. But they'd all belong to the same document. The NSSpellChecker keeps a separate ignored words list for each document that it checks. To help match ignored words lists to documents, you should call uniqueSpellDocumentTag once for each document. This method returns a unique arbitrary integer that will serve to distinguish one document from the others being checked and to match each ignored words list to a document. When searching for misspelled words, pass the tag as the fourth argument of checkSpellingOfString:startingAt:language:wrap:inSpellDocumentWithTag:wordCout:. (The convenience method checkSpellingOfString:startingAt: takes no tag. This method is suitable when the first responder does not conform to the NSIgnoreMisspelledWords protocol.)

When the application saves a document, it may choose to retrieve the ignored words list and save it along with the document. To get back the right list, it must send the NSSpellChecker an ignoredWordsInSpellDocumentWithTag: message. When the application has closed a document, it should notify the NSSpellChecker that the document's ignored words list can now be discarded, by sending it a closeSpellDocumentWithTag: message. When the application reopens the document, it should restore the ignored words list with the message setIgnoredWords:inSpellDocumentWithTag:.

Making a Checker available

• + (NSSpellChecker *)sharedSpellChecker Returns the NSSpellChecker (one per application).
• + (BOOL)sharedSpellCheckerExists Returns whether the application's NSSpellChecker has already been created.

• - (NSView *)accessoryView Returns the Spelling panel's accessory NSView object.
• - (void)setAccessoryView:(NSView *)aView Makes an NSView object an accessory of the Spelling panel by making it a subview of the panel's content view. This method posts the notification NSWindowDidResizeNotification with the Spelling panel object to the default notification center.
• - (NSPanel *)spellingPanel Returns the NSSpellChecker's panel.

• - (int)countWordsInString:(NSString *)aString Returns the number of words in string. The language language:(NSString *)language argument specifies the language used in the string. If language is the empty string, the current selection in the Spelling panel's pop-up menu is used.
• - (NSRange)checkSpellingOfString:(NSString *)stringToCheck startingAt:(int)startingOffset Starts the search for a misspelled word in stringToCheck starting at startingOffset within the string object. Returns the range of the first misspelled word. Wrapping occurs but no ignored-words dictionary is used.
• - (NSRange)checkSpellingOfString:(NSString *)stringToCheck startingAt:(int)startingOffset Starts the search for a misspelled word in stringToCheck language:(NSString *)language starting at startingOffset within the string object. wrap:(BOOL)wrapFlag Returns the range of the first misspelled word and inSpellDocumentWithTag:(int)tag optionally the word count by reference. tag is an wordCount:(int *)wordCount identifier unique within the application used to inform the spell check which document (actually, a dictionary) of ignored words to use. wrapFlag determines whether spell checking continues at the beginning of the string when the end is reached. language is the language used in the string. If language is the empty string, the current selection in the Spelling panel's pop-up menu is used.

• - (NSString *)language Returns the current language used in spell-checking.
• - (BOOL)setLanguage:(NSString *)aLanguage Sets the language to use in spell-checking to aLanguage. Returns whether the Language pop-up list in the Spelling panel lists aLanguage.

• + (int)uniqueSpellDocumentTag Returns a guaranteed unique tag to use as the spell-document tag for a document. Use this method to generate tags to avoid collisions with other objects that can be spell-checked.
• - (void)closeSpellDocumentWithTag:(int)tag Notifies the NSSpellChecker that the user has finished with the ignored-word document identified by tag, causing it to throw that dictionary away.
• - (void)ignoreWord:(NSString *)wordToIgnore Instructs the NSSpellChecker to ignore all future inSpellDocumentWithTag:(int)tag occurrences of wordToIgnore in the document identified by tag. You should call this method from within your implementation of the NSIgnoreMisspelledWords protocol's ignoreSpelling:.
• - (NSArray *)ignoredWordsInSpellDocumentWithTag:(int)tag Returns the array of ignored words for a document identified by tag. Invoke this before closeSpellDocument: if you want to store the ignored words.
• - (void)setIgnoredWords:(NSArray *)someWords Initializes the ignored-words document (i.e., dictionary inSpellDocumentWithTag:(int)tag identified by tag with someWords, an array of words to ignore.
• - (void)setWordFieldStringValue:(NSString *)aString Sets the string that appears in the misspelled word field, using the string object aString.
• - (void)updateSpellingPanelWithMisspelledWord:(NSString *)word Causes NSSpellChecker to update the Spelling panel's misspelled-word field to reflect word. You are responsible for highlighting word in the document and for extracting it from the document using the range returned by the checkSpelling:... methods. Pass the empty string as word to have the system beep, indicating no misspelled words were found.