Finalizing the Book List Application
Our application is not complete until we can save, update and delete books. In this tutorial we will add this functionality.


Final Project

Download source


Let's get started with properties
We add a couple of properties first. The "doubleClickedSelectedRow" keeps track of the row index when a row is double clicked in the table view for editing. This way if another row is accidentally selected before the update button is clicked, the correct book will still be updated.

I have set the path to the desktop for convenience only. Change this to your liking.

Applescript:

property doubleClickedSelectedRow : -1
property FILE_PATH : POSIX path of ((path to desktop as string) & "BookList.plist")

AwakeFromNib
We add a double-click action to our table view to point to a handler we will create shortly. Next we either read in our saved data or load test data if no file is found. We use NSArray's "initWithContentsOfFile_" method to read in the file if it is found. NSArray is the parent class of NSMutableArray so we have all of its methods available to us.

Applescript:

on awakeFromNib()
   
   -- Set double-click action on table view
   aTableView's setDoubleAction_("tableDoubleClicked")
   
   set theDataSource to NSMutableArray's alloc()'s initWithContentsOfFile_(FILE_PATH)
   
   if theDataSource is equal to missing value then
       
       set theDataSource to NSMutableArray's alloc()'s init()
       set theData to {{bookTitle:"A Christmas Carol", theAuthor:"Charles Dickens", theStatus:1}, {bookTitle:"The Adventures of Huckleberry Finn", theAuthor:"Mark Twain", theStatus:1}, {bookTitle:"The Adventures of Tom Sawyer", theAuthor:"Mark Twain", theStatus:0}, {bookTitle:"War and Peace", theAuthor:"Leo Tolstoy", theStatus:0}}
       
       theDataSource's addObjectsFromArray_(theData)
   end if
   
   aTableView's reloadData()
end awakeFromNib

Double-click Action
We first check to see if the selectedRow is -1. If you double-click inside the table view in the blank space beneath the last row, the value of selectedRow will be -1.

If selectedRow is not -1, we retrieve the book from theDataSource array by its index, the value of selectedRow. To get the values from the book we use the NSDictionary's "valueForKey_" method. This is equivalent to the AppleScript method "get theStatus of thisBook" when getting values from a record.

The next few lines are setting the value of our properties that we bound to the value of the text fields and radio button matrix. You might think that you can set these properties with the following, but you would be mistaken.

Our properties have two methods created automatically for us, a getter and a setter. We use these methods to "get" and "set" their values. Since the properties are bound to the fields, double-clicking on a table row will insert those values in their respective fields.

Example Getter and Setter Methods in Objective-C

tableDoubleClicked Handler

Applescript:

on tableDoubleClicked()
   if aTableView's selectedRow as integer is not equal to -1 then
       my setDoubleClickedSelectedRow_(aTableView's selectedRow as integer)
       set thisBook to theDataSource's objectAtIndex_(doubleClickedSelectedRow as integer)
       my setTheStatus_(thisBook's valueForKey_("theStatus"))
       my setBookTitle_(thisBook's valueForKey_("bookTitle"))
       my setTheAuthor_(thisBook's valueForKey_("theAuthor"))
   end if
end tableDoubleClicked

Updating Our Book
Updating our book is very simple. We gather the information into a record the same as we do when creating a new book and then replace the book being updated with the new one.

We use NSMutableArray's "replaceObjectAtIndex_withObject_" method to accomplish this task. Next we reload the table view and update our file using "writeToFile" which we will write next.

Applescript:

on updateBookInfo_(sender)
   tell bookTitleField to selectText_(me) -- forces all fields to complete editing so that our properties are up to date ( thanks Shane Stanley )
   if my checkFields() then
       return
   end if
   set updatedBook to {bookTitle:bookTitle, theAuthor:theAuthor, theStatus:theStatus}
   theDataSource's replaceObjectAtIndex_withObject_(doubleClickedSelectedRow as integer, updatedBook)
   aTableView's reloadData()
   my writeToFile()
   my clearFields()
end updateBookInfo_

Saving Our Book List Data
Saving to file is very simple. We use the NSArray's "writeToFile_atomically_" method. It returns "YES" if successful and "NO" if not. If there was an error we display a dialog.

The "writeToFile_atomically_" writes a "plist" file. As you can see below, our BookList.plist file contains an array of dictionaries holding our data structure.

At first this looks strange but it is actually very well organized and easy to read. Every book item is one dictionary inside the array and each dictionary contains key-value pairs of our data.

Click to see larger image

ImageTitle

Applescript:

on writeToFile()
   if not theDataSource's writeToFile_atomically_(FILE_PATH, true) then
       set messageText to "There was an error writing to file"
       display dialog messageText buttons {"Ok"} default button 1
   end if
end writeToFile

Also add these methods

Applescript:

on clearFields()
   -- Clear fields
   bookTitleField's setStringValue_("")
   authorField's setStringValue_("")
   
   -- Clear property variables
   setTheAuthor_("")
   setBookTitle_("")
end clearFields


on checkFields()
   set missingValues to false
   repeat with anItem in {theAuthor, bookTitle}
       if anItem is in {"", missing value} then
           set missingValues to true
           display dialog "The Title and/or Author fields are empty!" with icon 0 buttons {"Ok"} default button 1
           return
       end if
   end repeat
   return missingValues
end checkFields

Removing a Book from the list
Removing a book from the list is simple as well. We first check that a row is selected and then perform the NSMutableArray's "removeObjectAtIndex_" method passing it the selected row index. We then reload the table data to reflect our deletion and update our saved file as well.

Applescript:

on removeBookFromList_(sender)
   if aTableView's selectedRow as integer is not equal to -1 then
       theDataSource's removeObjectAtIndex_(aTableView's selectedRow as integer)
       aTableView's reloadData()
       my writeToFile()
       my clearFields()
   end if
end removeBookFromList_

Update addData Method
Add the following two lines in the "addData" method.

Applescript:

-- add to first line
tell bookTitleField to selectText_(me)

-- Add as last line
my writeToFile()

I added a handler to quit the application when the window closes
If you do not want this behavior you should create a way to open the window after it has been closed and remove the following code or return false.

Applescript:

on applicationShouldTerminateAfterLastWindowClosed_(sender)
   return true
end applicationShouldTerminateAfterLastWindowClosed_

The GUI
Add in the "Update" and "Delete" buttons and connect them to their respective handlers. I also made some minor adjustments to how the fields resize for a better user experience.

Final Code
Download source

Applescript:

property NSMutableArray : class "NSMutableArray"
property NSImage : class "NSImage"

script PartFourAppDelegate
   -- Inheritance
   -- Our class is a sub-class of NSObject
   property parent : class "NSObject"
   
   -- IBOutlets
   -- Interface Builder considers an outlet as any
   -- property with "missing value" as its initial value
   property aTableView : missing value
   property aWindow : missing value
   property bookTitleField : missing value
   property authorField : missing value
   property statusField : missing value
   
   -- Bindings
   property theAuthor : ""
   property bookTitle : ""
   property theStatus : ""
   
   -- Other properties
   property doubleClickedSelectedRow : -1
   property theDataSource : {}
   property FILE_PATH : POSIX path of ((path to desktop as string) & "BookList.plist")
   
   -- IBActions (button clicks)
   -- Interface Builder considers an action as any
   -- single parameter method ending with an underscore
   on addData_(sender)
       tell bookTitleField to selectText_(me) -- forces all fields to complete editing so that our properties are up to date ( thanks to Shane Stanley )
       if my checkFields() then
           return
       end if
       if theStatus is "" then
           set theStatus to 0
       end if
       set newData to {bookTitle:bookTitle, theAuthor:theAuthor, theStatus:theStatus}
       
       theDataSource's addObject_(newData)
       aTableView's reloadData()
       
       my clearFields()
       
       aWindow's makeFirstResponder_(bookTitleField)
       my writeToFile()
   end addData_
   
   on removeBookFromList_(sender)
       if aTableView's selectedRow as integer is not equal to -1 then
           theDataSource's removeObjectAtIndex_(aTableView's selectedRow as integer)
           aTableView's reloadData()
           my writeToFile()
           my clearFields()
       end if
   end removeBookFromList_
   
   on updateBookInfo_(sender)
       tell bookTitleField to selectText_(me)
       if my checkFields() then
           return
       end if
       set updatedBook to {bookTitle:bookTitle, theAuthor:theAuthor, theStatus:theStatus}
       theDataSource's replaceObjectAtIndex_withObject_(doubleClickedSelectedRow as integer, updatedBook)
       aTableView's reloadData()
       my writeToFile()
       my clearFields()
   end updateBookInfo_
   
   
   ##################################################
   # Methods
   
   on writeToFile()
       if not theDataSource's writeToFile_atomically_(FILE_PATH, true) then
           set messageText to "There was an error writing to file"
           display dialog messageText buttons {"Ok"} default button 1
       end if
   end writeToFile
   
   on clearFields()
       -- Clear fields
       bookTitleField's setStringValue_("")
       authorField's setStringValue_("")
       setTheAuthor_("")
       setBookTitle_("")
   end clearFields
   
   on checkFields()
       set missingValues to false
       repeat with anItem in {theAuthor, bookTitle}
           if anItem is in {"", missing value} then
               set missingValues to true
               display dialog "The Title and/or Author fields are empty!" with icon 0 buttons {"Ok"} default button 1
               return
           end if
       end repeat
       return missingValues
   end checkFields
   
   
   ##################################################
   # TableView
   
   on tableView_objectValueForTableColumn_row_(aTableView, aColumn, aRow)
       
       if theDataSource's |count|() is equal to 0 then return end
       
       set ident to aColumn's identifier
       
       set theRecord to theDataSource's objectAtIndex_(aRow)
       set theValue to theRecord's objectForKey_(ident)
       
       if ident's isEqualToString_("theStatus") then
           
           if theValue's intValue() = 0 then
               set theValue to NSImage's imageNamed_("green")
           else
               set theValue to NSImage's imageNamed_("red")
           end if
           
       end if
       
       return theValue
   end tableView_objectValueForTableColumn_row_
   
   on numberOfRowsInTableView_(aTableView)
       try
           if theDataSource's |count|() is equal to missing value then
               return 0
           else
               return theDataSource's |count|()
           end if
       on error
           return 0
       end try
   end numberOfRowsInTableView_
   
   on tableView_sortDescriptorsDidChange_(aTableView, oldDescriptors)
       set sortDesc to aTableView's sortDescriptors()
       theDataSource's sortUsingDescriptors_(sortDesc)
       aTableView's reloadData()
   end tableView_sortDescriptorsDidChange_
   
   on tableDoubleClicked()
       if aTableView's selectedRow as integer is not equal to -1 then
           my setDoubleClickedSelectedRow_(aTableView's selectedRow as integer)
           set thisBook to theDataSource's objectAtIndex_(doubleClickedSelectedRow as integer)
           my setTheStatus_(thisBook's valueForKey_("theStatus"))
           my setBookTitle_(thisBook's valueForKey_("bookTitle"))
           my setTheAuthor_(thisBook's valueForKey_("theAuthor"))
       end if
   end tableDoubleClicked
   
   
   
   ##################################################
   # Application
   
   on awakeFromNib()
       
       -- Set double-click action on table view
       aTableView's setDoubleAction_("tableDoubleClicked")
       
       set theDataSource to NSMutableArray's alloc()'s initWithContentsOfFile_(FILE_PATH)
       
       if theDataSource is equal to missing value then
           
           set theDataSource to NSMutableArray's alloc()'s init()
           set theData to {{bookTitle:"A Christmas Carol", theAuthor:"Charles Dickens", theStatus:1}, {bookTitle:"The Adventures of Huckleberry Finn", theAuthor:"Mark Twain", theStatus:1}, {bookTitle:"The Adventures of Tom Sawyer", theAuthor:"Mark Twain", theStatus:0}, {bookTitle:"War and Peace", theAuthor:"Leo Tolstoy", theStatus:0}}
           
           theDataSource's addObjectsFromArray_(theData)
       end if
       
       aTableView's reloadData()
   end awakeFromNib
   
   on applicationWillFinishLaunching_(aNotification)
       -- Insert code here to initialize your application before any files are opened
   end applicationWillFinishLaunching_
   
   on applicationShouldTerminate_(sender)
       theDataSource's release()
       return true
   end applicationShouldTerminate_
   
   on applicationShouldTerminateAfterLastWindowClosed_(sender)
       return true
   end applicationShouldTerminateAfterLastWindowClosed_
   
end script

Until next time, Happy coding!

Download source