10. MVC in Squeak

• Dependency Mechanisms in MVC
• Reaching the Dependents
• changed:
• changed:with:
• broadcast #someMessage
• broadcast #someMessage: with: aParameter
• Dependency Implementation
• All objects can have dependents!
• But kept in a global dictionary => SLOW!
• Models keep dependents in a local instance variable
• dependents
• UI without MVC: Menus
• Upon a mouse click...
• UI without MVC: Dialog
• FillInTheBlank request: 'User name:'
• Benefits of MVC
• Separates the UI from the underlying structure
• Views present some aspect of the Model. (Can be multiple views of same model.)
• Working out an Application in Squeak MVC
• PhoneBook Browser Dependencies
• PhoneBookBrowser
• Object subclass: #PhoneBookBrowser
• instanceVariableNames: 'phoneBook list listIndex listItem '
• classVariableNames: ''
• poolDictionaries: ''
• category: 'PhoneBook'!
• PhoneBookBrowser methodsFor: 'phone book access'
• phoneBook
• ^phoneBook
• phoneBook: aDictionary
• self validate: aDictionary.
• phoneBook := aDictionary.
• PhoneBookBrowser methodsFor: 'phone book access'
• validate: aPhoneBook
• "make sure the phone book is a dictionary with string keys and values"
• | errorMessage |
• errorMessage := 'invalid phone book'.
• (aPhoneBook isKindOf: Dictionary) ifFalse: [^self error: errorMessage].
• aPhoneBook associationsDo: [:anAssociation |
• ((anAssociation key isKindOf: String) & (anAssociation value isKindOf: String))
• ifFalse: [^self error: errorMessage]]
• PhoneBookBrowser methodsFor: 'change management'
• add: aString
• "The string is assumed to be of the form: 'key cr value'."
• | stream key value keyExists |
• stream := ReadStream on: aString.
• key := stream upTo: Character cr. value := stream upTo: nil.
• keyExists := true. phoneBook at: key ifAbsent: [keyExists := false].
• phoneBook at: key put: value.
• keyExists ifFalse: [
• self list: phoneBook keys.
• "Causes 'self update: #list', updates the list view's list."
• self listItem: key.
• "Causes 'self update: #listIndex', updates the list view's selection."]
• PhoneBookBrowser methodsFor: 'change management'
• remove: aString
• "String is assumed to be of the form: 'key cr value'."
• | key |
• key := aString copyUpTo: Character cr.
• phoneBook removeKey: key ifAbsent: [].
• self list: phoneBook keys. "Causes 'self update: #list', which updates list view's list."
• PhoneBookBrowser methodsFor: 'change management'
• retrieve
• "Returns 'key cr value' if an item was selected, otherwise the default."
• listItem isNil
• ifTrue: [^PhoneBookBrowser defaultEntry]
• ifFalse: [^listItem, (String with: Character cr), (phoneBook at: listItem)]
• PhoneBookBrowser methodsFor: 'selection management'
• list
• "Returns the list of entries"
• ^list
• list: aList
• "Sets the list of entries to aList (internally, keep this list sorted)."
• list := aList asSortedCollection asArray. listItem := nil.
• self changed: #list.
• listIndex
• "Returns the index into the currently selected entry."
• ^listItem isNil ifTrue: [^0] ifFalse: [^list indexOf: listItem].
• PhoneBookBrowser methodsFor: 'selection management'
• toggleListIndex: aListIndex
• "Selects the specified phone book entry if it was not already specified; otherwise, deselects it."
• self listIndex = aListIndex
• ifTrue: [listItem := nil]
• ifFalse: [listItem := list at: aListIndex].
• self changed: #listIndex.
• listItem
• "Returns the currently selected entry."
• ^listItem
• listItem: aString
• "Changes the currently selected entry."
• listItem := aString.
• self changed: #listIndex
• PhoneBookBrowser class methodsFor: 'querying'
• defaultEntry
• ^'LastName,FirstName Sample data' withCRs "There is a tab after the '\'"! !
• PhoneBookBrowser class methodsFor: 'opening'
• openOn: aPhoneBook
• "PhoneBookBrowser openOn: Dictionary new"
• | aBrowser topView aListView aStringHolder aTextView |
• aBrowser := self new phoneBook: aPhoneBook; list: aPhoneBook keys.
• topView := StandardSystemView new
• label: 'Phone Book';
• model: aBrowser;
• borderWidth: 1.
• aListView := PhoneBookListView new
• model: aBrowser;
• list: aBrowser list;
• borderWidth: 1.
• aStringHolder := StringHolder new contents: PhoneBookBrowser defaultEntry.
• aTextView := (PhoneBookTextView container: aStringHolder)
• borderWidth: 1.
• topView addSubView: aListView; addSubView: aTextView toRightOf: aListView.
• aBrowser addDependent: aTextView. "The list view is already a dependent"
• topView controller open.
• PhoneBookListView
• ListView subclass: #PhoneBookListView
• instanceVariableNames: ''
• classVariableNames: ''
• poolDictionaries: ''
• category: 'PhoneBook'
• PhoneBookListView methodsFor: 'controller access and display'
• defaultControllerClass
• ^ListController
• moveSelectionBox: aSelection
• super moveSelectionBox: aSelection. "Make the standard move"
• "If it's a deselection or it's visible, do nothing; otherwise, reposition."
• (aSelection = 0 or: [self selectionBox intersects: self clippingBox])
• ifFalse: [self positionList. self displayView].
• PhoneBookTextController
• StringHolderController subclass: #PhoneBookTextController
• instanceVariableNames: ''
• classVariableNames: 'PhoneBookTextControllerYellowButtonMenu PhoneBookTextControllerYellowButtonMessages '
• poolDictionaries: ''
• category: 'PhoneBook'
• PhoneBookTextController class methodsFor: 'initialize'
• initialize
• "Initializes the yellow button pop-up menu and corresponding messages."
• "Differs from StringHolderController menu by adding the 'remove' label."
• PhoneBookTextControllerYellowButtonMenu :=
• PopUpMenu
• labels: 'againundocopycutpastedoItprintItacceptcancelremove' withCRs
• lines: #(2 5 7).
• PhoneBookTextControllerYellowButtonMessages :=
• #(again undo copySelection cut paste doIt printIt accept cancel remove).
• PhoneBookTextController methodsFor: 'menu messages'
• accept
• "Accepts the text in the view (for insertion)."
• | string aPhoneBookBrowser |
• string := paragraph string. "Note: this is how 'super accept' accesses the text.
• We can't say 'model contents' because the text has not yet been accepted."
• (string includes: Character cr)
• ifTrue: [super accept "Unlocks the model"]
• ifFalse: [^3 timesRepeat: [view flash "illegal"]].
• "Temporarily hide the scrollbars to prevent them from being overwritten by the changing list view"
• self controlTerminate.
• "Make the change to the browser."
• aPhoneBookBrowser := view topView model. aPhoneBookBrowser add: string.
• "Restore the scrollbars."
• self controlInitialize.
• PhoneBookTextController methodsFor: 'menu messages'
• remove
• "Accepts the text in the view (for removal)."
• | string aPhoneBookBrowser |
• string := paragraph string. "Not: this is how 'super accept' accesses the text. We can't say 'model contents' because the text has not yet been accepted."
• (string includes: Character cr)
• ifTrue: [super accept "Unlocks the model"]
• ifFalse: [^3 timesRepeat: [view flash "illegal"]].
• "Temporarily hide the scrollbars to prevent them from being overwritten by the changing list view"
• self controlTerminate.
• "Make the change to the browser."
• aPhoneBookBrowser := view topView model. aPhoneBookBrowser remove: string.
• "Restore the scrollbars."
• self controlInitialize.
• PhoneBookTextController methodsFor: 'initialize'
• initializeYellowButtonMenu
• self yellowButtonMenu: PhoneBookTextControllerYellowButtonMenu
• yellowButtonMessages: PhoneBookTextControllerYellowButtonMessages
• PhoneBookTextView
• StringHolderView subclass: #PhoneBookTextView
• instanceVariableNames: ''
• classVariableNames: ''
• poolDictionaries: ''
• category: 'PhoneBook'!
• PhoneBookTextView methodsFor: 'controller and updating'
• defaultControllerClass
• ^PhoneBookTextController
• update: aParameter
• | aPhoneBookBrowser |
• aParameter == #listIndex ifTrue: [
• aPhoneBookBrowser := self topView model.
• self model contents: aPhoneBookBrowser retrieve.
• super update: #model "Also update the view itself"].