Simple question: where do the tableView and section arguments get passed from? The actual code in the method return [self.listData count]; doesn't even mention them.
Here's my interface code:
#interface Simple_TableViewController : UIViewController
<UITableViewDelegate, UITableViewDataSource>
{
NSArray *listData;
}
#property (nonatomic, retain) NSArray *listData;
#end
And this is all the implementation code:
#import "Simple_TableViewController.h"
#implementation Simple_TableViewController
#synthesize listData;
- (void)viewDidLoad {
NSArray *array = [[NSArray alloc] initWithObjects:#"Sleepy", #"Sneezy",
#"Bashful", #"Happy", #"Doc", #"Grumpy", #"Dopey", #"Thorin",
#"Dorin", #"Nori", #"Ori", #"Balin", #"Dwalin", #"Fili", #"Kili",
#"Oin", #"Gloin", #"Bifur", #"Bofur", #"Bombur", nil];
self.listData = array;
[array release];
[super viewDidLoad];
}
- (void)viewDidUnload {
self.listData = nil;
}
- (void)dealloc {
[listData release];
[super dealloc];
}
#pragma mark -
#pragma mark Table View Data Source Methods
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section {
return [self.listData count];
}
I just want to know how does the method (NSInteger)tableView: (UITableView *)numberOfRowsInSection: receive those arguments? Of course this happens everywhere; I just want to understand it.
The Simple_TableViewController class is likely meant to manage a single table with a single section. Given that, the tableView and section parameters aren't important because they can only be one thing: a pointer to the table and 0, respectively.
Your view controller class is adding support for these callback methods through UITableViewDelegate and UITableViewDataSource. You are adding this support in your .h file through <UITableViewDelegate, UITableViewDataSource>. These classes are built in to the Cocoa Touch framework and you are just using them. When the table is (re)loaded, this callback methods are called if you have defined them (some are required, others are optional).
Related
I am trying to set the value of an NSTextField, but it's not working properly.
I have a button linked to an IBAction, and when I set it using self, it works fine:
#import <Foundation/Foundation.h>
#interface TestMessage : NSObject {
IBOutlet NSTextField *text;
}
- (IBAction) setMessage: (id) controller;
- (void) Message:(NSString *) myMessage;
#end
#import "TestMessage.h"
#implementation TestMessage
- (IBAction) setMessage: (id) controller {
// This works
[self Message:#"Hello"];
// but this doesn't
TestMessage * messageTest= [TestMessage new];
[messageTest Message:#"Hi"];
}
- (void) Message: (NSString *) myMessage {
[text setStringValue: myMessage];
NSLog(#"Message Was Called");
// This returns <NSTextField: 0x1001355b0> when called
// using self, but null when called the other way.
NSLog(#"%#", text);
}
#end
I've searched for a while, but still can't find the answer.
I guess it has something to do with the delegate, but I'm not sure.
Thanks in advance.
Are you sure message is called when you call it from anotherFuntion? If anotherFuntion is a method of another class, calling [self message:] won't work as you expected to...
I know this is an old post, but I have been fiddling with the same issue today.
You have to return string value in textfield:
[textField stringValue];
The code
TestMessage * messageTest = [TestMessage new];
is unusual, specifically new. I'm going to assume that new is just a class method does normal alloc/init equivalent to
TestMessage * messageTest = [[TestMessage alloc] init];
The main problem is that IBOutlet NSTextField *text will be initialized only if the class TestMessage is loaded with a Nib file. It would have to be named as the class of an object in Interface Builder, like so
and you would have to implement initWithCoder and encodeWithCoder something like this in order to extract your field value from the IB encoding:
- (instancetype)initWithCoder:(NSCoder *)coder {
self = [super initWithCoder:coder];
if (self) {
self.text = [coder decodeObjectForKey:#"text"];
}
return self;
}
-(void)encodeWithCoder:(NSCoder *)coder
{
[super encodeWithCoder:coder];
[coder encodeObject:self.text forKey:#"text"];
}
Fundamentally, IBOutlet fields do not get wired up wherever you create an instance of that class. If they did, how would you express that field A should be wired to UI object A and field B should be wired to UI object B? The connection is established only in the context of loading a class from a Nib file.
I'm new to objective-c and I'm finding that I don't know how to correctly assert that a text property on some given label is equal to a raw string value. I'm not sure if I just need to cast the label as NSString or if I need to modify my assert statement directly.
#interface MoreTest : SenTestCase {
MagiczzTestingViewController* controller;
}
- (void) testObj;
#end
#implementation MoreTest
- (void) setUp
{
controller = [[MagiczzTestingViewController alloc] init];
}
- (void) tearDown
{
[controller release];
}
- (void) testObj
{
controller.doMagic;
STAssertEquals(#"hehe", controller.label.text, #"should be hehe, was %d instead", valtxt);
}
#end
The implementation of my doMagic method is below
#interface MagiczzTestingViewController : UIViewController {
IBOutlet UILabel *label;
}
#property (nonatomic, retain) UILabel *label;
- (void) doMagic;
#end
#implementation MagiczzTestingViewController
#synthesize label;
- (void) doMagic
{
label.text = #"hehe";
}
- (void)dealloc {
[label release];
[super dealloc];
}
#end
The build is fine when I modify the assert to compare a raw NSString to another but when I try to capture the text value (assuming it's of type NSString) it fails. Any help would be much appreciated!
STAssertEquals() checks for identity of the two values provided, so it's equivalent to doing this:
STAssertTrue(#"hehe" == controller.label.text, ...);
Instead, you want STAssertEqualObjects(), which will actually run an isEqual: check like the following:
STAssertTrue([#"hehe" isEqual:controller.label.text], ...);
You need to load the nib of the view controller. Otherwise there won't be any objects for the label outlet to be hooked up to.
One way to do this is to add an ivar for the view controller's view to your test case:
#interface MoreTest : SenTestCase {
MagiczzTestingViewController *controller;
UIView *view;
}
#end
#implementation MoreTest
- (void)setUp
{
[super setUp];
controller = [[MagiczzTestingViewController alloc] init];
view = controller.view; // owned by controller
}
- (void)tearDown
{
view = nil; // owned by controller
[controller release];
[super tearDown];
}
- (void)testViewExists
{
STAssertNotNil(view,
#"The view controller should have an associated view.");
}
- (void)testObj
{
[controller doMagic];
STAssertEqualObjects(#"hehe", controller.label.text,
#"The label should contain the appropriate text after magic.");
}
#end
Note that you also need to invoke super's -setUp and -tearDown methods appropriately from within yours.
Finally, do not use dot syntax for method invocation, it is not a generic replacement for bracket syntax in message expressions. Use dot syntax only for getting and setting object state.
I've been stuck on this for days and each time I come back to it I keep making my code more and more confusing to myself, lol. Here's what I'm trying to do. I have table list of charges, I tap on one and brings up a model view with charge details. Now when the model is presented a object is created to fetch a XML list of users and parses it and returns a NSMutableArray via a custom delegate. I then have a button that presents a picker popover, when the popover view is called the user array is used in an initWithArray call to the popover view. I know the data in the array is right, but when [pickerUsers count] is called I get an EXC_BAD_ACCESS. I assume it's a memory/ownership issue but nothing seems to help. Any help would be appreciated.
Relevant code snippets:
Charge Popover (Charge details model view):
#interface ChargePopoverViewController .....
NSMutableArray *pickerUserList;
#property (nonatomic, retain) NSMutableArray *pickerUserList;
#implementation ChargePopoverViewController
#synthesize whoOwesPickerButton, pickerUserList;
- (void)viewDidLoad {
JEHWebAPIPickerUsers *fetcher = [[JEHWebAPIPickerUsers alloc] init];
fetcher.delegate = self;
[fetcher fetchUsers];
}
-(void) JEHWebAPIFetchedUsers:(NSMutableArray *)theData {
[pickerUserList release];
pickerUserList = theData;
}
- (void) pickWhoPaid: (id) sender {
UserPickerViewController* content = [[UserPickerViewController alloc] initWithArray:pickerUserList];
UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:content];
[popover presentPopoverFromRect:whoPaidPickerButton.frame inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
content.delegate = self;
}
User Picker View Controller
#interface UserPickerViewController .....
NSMutableArray *pickerUsers;
#property(nonatomic, retain) NSMutableArray *pickerUsers;
#implementation UserPickerViewController
#synthesize pickerUsers;
-(UserPickerViewController*) initWithArray:(NSMutableArray *)theUsers {
self = [super init];
if ( self ) {
self.pickerUsers = theUsers;
}
return self;
}
- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component {
// Dies Here EXC_BAD_ACCESS, but NSLog(#"The content of array is%#",pickerUsers); shows correct array data
return [pickerUsers count];
}
I can provide additional code if it might help. Thanks in advance.
You declare the ivar holding the array as this...
#property (nonatomic, retain) NSMutableArray *pickerUserList;
But then you have a method implemented like this:
-(void) JEHWebAPIFetchedUsers:(NSMutableArray *)theData {
[pickerUserList release];
pickerUserList = theData;
}
You aren't retaining theData and you aren't calling the synthesized setter. If you did Build and Analyze, it should catch this problem and tell you about it. If not, file a bug.
I have a class called "CardSet", containing an NSMutableArray* cardSet to hold "cards", which I extend to make "DeckCards". I'd like "CardSet" to have a method called "(void)addCard:(Card*)" (and similarly a method "removeCard"). I'd like "addCard" to some how have access to and set cardSet. Even better I'd like to use the "addCard" method to initialise cardSet. The class file "CardSet.h" reads:
#import < Cocoa/Cocoa.h >
#import < Card.h >
#interface CardSet : NSObject {
NSMutableArray* cardSet;
}
-(id)init;
-(NSMutableArray*)getCardSet;
-(void)setCardSet:(NSMutableArray *)new_cardset;
-(Card*)getCard:(NSInteger) index;
**-(void)addCard:(Card*) new_card;**
-(void)removeCard:(Card*) old_card;
-(void)dealloc;
#property (readwrite, retain, getter=getCardSet, setter=setCardSet) NSMutableArray* cardSet;
#end
and the method file reads:
#import "CardSet.h"
#implementation CardSet
-(id)init{
if( self = [super init] ){} //will add initialisations here later
return self;
}
-(NSMutableArray*)getCardSet{
return cardSet;
}
-(void)setCardSet:(NSMutableArray *)new_cardSet{
cardSet = new_cardSet;
}
-(Card*)getCard:(NSInteger)index{
return [cardSet objectAtIndex:index];
}
**-(void)addCard:(Card *)new_card{
[cardSet addObject:new_card];
}**
-(void)removeCard:(Card *)old_card{
[cardSet removeObject:old_card];
}
-(void)dealloc{
[cardSet release];
[super dealloc];
}
#synthesize cardSet;
#end
This compiles just fine. I'd like to initialise a "DeckCards" instance using its "addCard" method 52 times. When I call addCard 52 times in a DeckCards setter method, and ask for the size of its "cardSet", I'm returned 0.
This appears to be a scope or privileges problem? Can the "addCard" method have any setter privileges? Must a setter argument be the same as the return and respective member type?
[I can work around the above by creating an NSMutableArray object "deck_cards_temp" outside of "DeckCard", add 52 cards to this, and pass it to set the member of my "DeckCards" instance via the setter inherited from "CardSet". This is not very satisfactory!]
What do you advise? Many thanks in advance for your help and patience.
You are never actually creating the cardSet object. You should be creating it in your -init method:
-(id)init
{
if( self = [super init] )
{
cardSet = [[NSMutableArray alloc] init];
}
return self;
}
Because you never actually create the array, all the calls to -addCard: are being sent to a nil object.
When you pass in an array to -setCardSet:, you are passing in an initialized array so the array is no longer nil and the -addCard: calls work fine.
CardSet.h
#import <Cocoa/Cocoa.h>
// For know we just need to know there is a class named "Card" being used but implemented later
#class Card;
#interface CardSet : NSObject {
NSMutableArray *cardSet;
}
// Here are the methods according to "correct" naming conventions
- (Card *)cardAtIndex:(NSInteger)index;
- (void)addCard:(Card *)card;
- (void)removeCard:(Card *)card;
// This will help us and forget about writing the setter/getter
#property (nonatomic, retain) NSMutableArray *cardSet;
#end
CardSet.m
#import "CardSet.h"
// Now we tell the compiler what "Card" is and what methods etc. it has
#import "Card.h"
#implementation CardSet
#synthesize cardSet;
- (id)init {
if (self = [super init]) {
// If we don't create the cardSet, how are we able to work with it!?
NSMutableArray *anArray = [[NSMutableArray alloc] init];
self.cardSet = anArray;
[anArray release];
}
return self;
}
- (Card *)cardAtIndex:(NSInteger)index {
return [cardSet objectAtIndex:index];
}
- (void)addCard:(Card *)card {
[cardSet addObject:card];
}
- (void)removeCard:(Card *)card {
[cardSet removeObject:card];
}
- (void)dealloc {
[cardSet release];
[super dealloc];
}
#end
As Abizern already noted: Naming the array the same as your class is a bad thing.
I would shorten that init method:
- (id)init {
if (self = [super init]) {
// If we don't create the cardSet, how are we able to work with it!?
self.cardSet = [NSMutableArray array];
}
return self;
}
If I have a custom class called Tires:
#import <Foundation/Foundation.h>
#interface Tires : NSObject {
#private
NSString *brand;
int size;
}
#property (nonatomic,copy) NSString *brand;
#property int size;
- (id)init;
- (void)dealloc;
#end
=============================================
#import "Tires.h"
#implementation Tires
#synthesize brand, size;
- (id)init {
if (self = [super init]) {
[self setBrand:[[NSString alloc] initWithString:#""]];
[self setSize:0];
}
return self;
}
- (void)dealloc {
[super dealloc];
[brand release];
}
#end
And I synthesize a setter and getter in my View Controller:
#import <UIKit/UIKit.h>
#import "Tires.h"
#interface testViewController : UIViewController {
Tires *frontLeft, *frontRight, *backleft, *backRight;
}
#property (nonatomic,copy) Tires *frontLeft, *frontRight, *backleft, *backRight;
#end
====================================
#import "testViewController.h"
#implementation testViewController
#synthesize frontLeft, frontRight, backleft, backRight;
- (void)viewDidLoad {
[super viewDidLoad];
[self setFrontLeft:[[Tires alloc] init]];
}
- (void)dealloc {
[super dealloc];
}
#end
It dies after [self setFrontLeft:[[Tires alloc] init]] comes back. It compiles just fine and when I run the debugger it actually gets all the way through the init method on Tires, but once it comes back it just dies and the view never appears. However if I change the viewDidLoad method to:
- (void)viewDidLoad {
[super viewDidLoad];
frontLeft = [[Tires alloc] init];
}
It works just fine. I could just ditch the setter and access the frontLeft variable directly, but I was under the impression I should use setters and getters as much as possible and logically it seems like the setFrontLeft method should work.
This brings up an additional question that my coworkers keep asking in these regards (we are all new to Objective-C); why use a setter and getter at all if you are in the same class as those setters and getters.
You have declared frontLeft as a 'copy' property:
#property (nonatomic,copy) Tires *frontLeft, *frontRight, *backleft, *backRight;
When you assign to this property, a copy is made by invoking the object's copy method. This only works for objects which support the NSCopying protocol (i.e., which implement a copyWithZone: method). Since your Tires class does not implement this method, you get an exception.
You probably want to change this to be a 'retain' property:
#property (nonatomic,retain) Tires *frontLeft, *frontRight, *backleft, *backRight;
See the Objective C documentation on declared properties for more on property declarations.
One problem that i see is here:
- (void)viewDidLoad {
[super viewDidLoad];
[self setFrontLeft:[[Tires alloc] init]];
}
When you call [Tires alloc] you get back an object with a retain count of 1. You then use a set method which you have synthesized, which bumps the retain count to 2. When your object is done with the Tire object, it will reduce the retain count back to 1, but the tire will never get deallocated. I think you should use:
[self setFrontLeft:[[[Tires alloc] init] autorelease]];