Mobile Application Programming. Messaging and Delegation

Transcription

1 Mobile Application Programming Messaging and Delegation

2

3 Color Chooser

4 Color Chooser MFColorChooserView UIControl or UIView MFColorChooserWheelView UIControl MFColorChooserValueSliderView UIControl MFColorChooserAlphaSliderView UIControl MFColorChooserSelectionView UIButton subclass MFColorChooserIndicatorView UIView

5 Problem: 2 Objects Talking Object 1 Object 2

6 Problem: 2 Objects Talking? Object 1 Object 2

7 Target-Action Regular Pointer Switch

8 Target-Action Regular Pointer addtarget...: Pointer Switch

9 Target-Action Regular Pointer Switch addtarget...: Pointer UIControlValueChanged

10 Target-Action Regular Pointer value addtarget...: Pointer Switch

11 Delegates Regular Pointer Table View

12 Delegates The Table View s Delegate Regular Pointer Table View Delegate Pointer setdatasource:self

13 Delegates The Table View s Delegate Regular Pointer reloaddata Delegate Pointer Table View

14 Delegates The Table View s Delegate Regular Pointer Table View Delegate Pointer rowsinsection:

15 Delegates The Table View s Delegate Regular Pointer Table View Delegate Pointer rowsinsection: returns 4

16 Delegates The Table View s Delegate Regular Pointer Table View Delegate Pointer cellforindexpath:

17 Delegates The Table View s Delegate Regular Pointer Table View Delegate Pointer cellforindexpath: returns cell

18 Delegates Assist in a task that a class doesn t know how to do itself, and thus an alternative to subclassing complex classes Also useful for sending messages from a class to it s containing class

19 Delegates Assist in a task that a class doesn t know how to do itself, and thus an alternative to subclassing complex classes Also useful for sending messages from a class to it s containing class

20 Delegates UIApplication applicationdidfinishlaunching: UIApplicationDelegate buildui

21 Delegates Assist in a task that a class doesn t know how to do itself, and thus an alternative to subclassing complex classes Also useful for sending messages from a class to it s containing class ComplexClass ContainedClass Delegate

22 Delegates A delegate is an object that performs actions on the behalf of another object A common use of them is a view object having a controller object interact with the program data model on it s behalf when the user triggers events Another use is a data model object alerting a controller of changes to it s data, which then tells view objects about the change 10 lines of code are required to properly set up both sides of a delegate connection between two objects

23 Function to be called on delegate Pointer to delegate object Implementation of get and set delegate methods Accessor to change delegate Called by the delegate with self as the parameter A call on this function... Function call on the delegate object, alerting it of some occurrence

24 Declaration that the class conforms to the delegate protocol Pointer to object (Has Relationship) The class uses the accessor to set itself as the delegate of the object... ends up here. Function that is called by the object on it s delegate Stuff the function does when the object alerts that colorselected happened

25 Application

26 Model View (MVC) Application

27 Notification How do these happen?

28 Delegates How do these happen? Delegates!

29 Has Weak Reference Delegate View Model Main (App Delegate) Example Program Structure Surface View List View Surface View Shape Collection UITableView

30 Has Weak Reference Delegate View Model Main (App Delegate) Delegate Interaction Example Surface View List View Surface View Shape Collection UITableView User Deletes a Shape Row

31 Has Weak Reference Delegate View Model Main (App Delegate) Delegate Interaction Example Surface View List View Table View Tells it s Delegate of the Deletion Surface View Shape Collection UITableView

32 Has Weak Reference Delegate View Model Main (App Delegate) Delegate Interaction Example List Deletes the Corresponding Shape in the Data Model Surface View List View Surface View Shape Collection UITableView

33 Has Weak Reference Delegate View Model Main (App Delegate) Delegate Interaction Example Surface View List View Surface View Shape Collection The Shape Collection Alerts it s Delegate of the Change to it s Data UITableView

34 Has Weak Reference Delegate View Model The Main Tells All View s that they Should Update Their Views Main (App Delegate) Delegate Interaction Example Surface View List View Surface View Shape Collection UITableView

35 Has Weak Reference Delegate View Model Main (App Delegate) Delegate Interaction Example Surface View The View s Update Their Views by Asking the Data Model for the Latest Data List View Surface View Shape Collection UITableView