iOS FAQ's Dynamic modification Uinavigationcontroller's Rightbarbuttonitem title

1. Initialization

In Viewdidload, add a button named "Add Columns" for Navigationitem

-(void) viewdidload{    [Super viewdidload];//do any additional setup after loading the view.        Self.navigationItem.rightBarButtonItem.title = @ "Add columns";    [Self.navigationItem.rightBarButtonItem Initwithbarbuttonsystemitem:uibarbuttonsystemitemundo                                                                 target:self                                                                 Action: @selector (Myaction)];        }

2. Attempt to change the button name failed attempts to modify the name of the button in the following manner, but failed

-(void) OnSelectionChanged: (ID) selection{    self.navigationItem.rightBarButtonItem.title = @ "edit";     }

3. Cause analysis

Why is the title of the Backbarbuttonitem set directly invalid?

View the Title Property description of the parent class uibaritem of the Apple document Uibarbuttonitem:

You should set before adding the item to a bar. The default value is nil. Therefore, the title cannot be modified, only the control itself can be reset.

4. Correct code 4.1 The idea of a single modification of the title is not, should I call the initialization method again? The code is as follows, eventually still no ah, no words

Self.navigationItem.rightBarButtonItem.title = @ "edit"; [Self.navigationItem.rightBarButtonItem initWithBarButtonSystemItem:UIBarButtonSystemItemUndotarget:selfaction: @selector (myaction)];

4.1 Thinking two since only the title does not work, then the whole button to replace it! Create a new button, replace Self.navigationItem.rightBarButtonItem with this new button, this time finally, thank goodness!!!

Uibarbuttonitem *temporarybarbuttonitem = [[Uibarbuttonitem alloc] Initwithbarbuttonsystemitem: Uibarbuttonsystemitemundo                                                                    target:self                                                                    Action: @selector (Changewellcolumnaction)];    Temporarybarbuttonitem.title = @ "edit";    Self.navigationItem.rightBarButtonItem = Temporarybarbuttonitem;    [Temporarybarbuttonitem release];

5. Summary of the problem in the idea of a failure of the reasons or not to find, thinking two have no side-effect is not very clear, welcome to the great God of all the way to enlighten!!!

iOS FAQ's Dynamic modification Uinavigationcontroller's Rightbarbuttonitem title