- •C and Objective-C
- •How this book works
- •How the life of a programmer works
- •Installing Apple’s developer tools
- •Getting started with Xcode
- •Where do I start writing code?
- •How do I run my program?
- •So what is a program?
- •Don’t stop
- •Types
- •A program with variables
- •Challenge
- •Boolean variables
- •When should I use a function?
- •How do I write and use a function?
- •How functions work together
- •Local variables, frames, and the stack
- •Recursion
- •Looking at the frames in the debugger
- •return
- •Global and static variables
- •Challenge
- •printf()
- •Integer operations
- •Integer division
- •Operator shorthand
- •Floating-point numbers
- •Tokens for displaying floating-point numbers
- •The while loop
- •The for loop
- •break
- •continue
- •The do-while loop
- •Challenge
- •Getting addresses
- •Storing addresses in pointers
- •Getting the data at an address
- •How many bytes?
- •NULL
- •Stylish pointer declarations
- •Challenges
- •Writing pass-by-reference functions
- •Avoid dereferencing NULL
- •Creating and using your first object
- •Message anatomy
- •Objects in memory
- •Challenge
- •Nesting message sends
- •Multiple arguments
- •Sending messages to nil
- •Challenge
- •Challenge
- •NSMutableArray
- •Reference pages
- •Quick Help
- •Other options and resources
- •Accessor methods
- •Dot notation
- •Properties
- •self
- •Multiple files
- •Challenge
- •Overriding methods
- •super
- •Challenge
- •Object ownership and ARC
- •Creating the Asset class
- •Adding a to-many relationship to Employee
- •Challenge
- •Retain cycles
- •Weak references
- •Zeroing of weak references
- •For the More Curious: Manual reference counting and ARC History
- •Retain count rules
- •NSArray/NSMutableArray
- •Immutable objects
- •Sorting
- •Filtering
- •NSSet/NSMutableSet
- •NSDictionary/NSMutableDictionary
- •Preprocessor directives
- •#include and #import
- •#define
- •Global variables
- •enum
- •#define vs global variables
- •Writing an NSString to a file
- •Reading files with NSString
- •Writing an NSData object to a file
- •Reading an NSData from a file
- •Target-action
- •Helper objects
- •Notifications
- •Which to use?
- •Callbacks and object ownership
- •Challenge
- •Getting started with iTahDoodle
- •BNRAppDelegate
- •Adding a C helper function
- •Objects in iTahDoodle
- •Model-View-Controller
- •The application delegate
- •Setting up views
- •Running on the iOS simulator
- •Wiring up the table view
- •Adding new tasks
- •Saving task data
- •For the More Curious: What about main()?
- •Edit BNRDocument.h
- •A look at Interface Builder
- •Edit BNRDocument.xib
- •Making connections
- •Revisiting MVC
- •Edit BNRDocument.m
- •Writing init methods
- •A basic init method
- •Using accessors
- •init methods that take arguments
- •Deadly init methods
- •Property attributes
- •Mutability
- •Lifetime specifiers
- •copy
- •More about copying
- •Advice on atomic vs. nonatomic
- •Key-value coding
- •Non-object types
- •Defining blocks
- •Using blocks
- •Declaring a block variable
- •Assigning a block
- •Passing in a block
- •typedef
- •Return values
- •Memory management
- •The block-based future
- •Challenges
- •Anonymous block
- •NSNotificationCenter
- •Bitwise-OR
- •Bitwise-AND
- •Other bitwise operators
- •Exclusive OR
- •Complement
- •Left-shift
- •Right-shift
- •Using enum to define bit masks
- •More bytes
- •Challenge
- •char
- •char *
- •String literals
- •Converting to and from NSString
- •Next Steps
- •Index
Adding new tasks
Adding new tasks
When you created the UIButton instance in application:didFinishLaunchingWithOptions:, you gave it a target/action pair:
[insertButton addTarget:self action:@selector(addTask:)
forControlEvents:UIControlEventTouchUpInside];
The target is self, and the action is addTask:. So the Insert button sends the BNRAppDelegate the addTask: message. Thus, we need to implement the addTask: method in BNRAppDelegate.m.
- (void)addTask:(id)sender
{
// Get the to-do item
NSString *t = [taskField text];
//Quit here if taskField is empty if ([t isEqualToString:@""]) {
return;
}
//Add it to our working array [tasks addObject:t];
//Refresh the table so that the new item shows up [taskTable reloadData];
//And clear out the text field
[taskField setText:@""]; // Dismiss the keyboard
[taskField resignFirstResponder];
}
What’s this resignFirstResponder business? Here’s the short version:
Some view objects are also controls – views that the user can interact with. Buttons, sliders, and text fields are examples of controls. When there are controls on the screen, one of them can be the first responder. Having first responder status means that the control gets dibs on handling any text input from the keyboard or any shake events (such as “Shake to Undo”).
When the user taps a control that can accept first responder status, that control is sent the becomeFirstResponder message. Until another control becomes the first responder or the current control is sent the resignFirstResponder message, that control will keep this status and receive keyboard and shake input.
When a text input control (like a text field) becomes the first responder, the keyboard materializes on the screen. As long as the current first responder is a control that accepts text input, the keyboard will remain on the screen. At the end of addTask:, we tell the text field to resign its status, which causes the keyboard to dematerialize.
Build and run the application. Now you can add tasks!
Saving task data
There is one final feature that you’ll add to iTahDoodle. Naturally, when users quit the app, they’d like their to-do lists to stick around for later.
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