I keep reading that dot syntax is possible but I keep getting errors that the struct does not contain members I am referencing. Perhaps its not the dot syntax so I have included details of what I am doing in hopes of a solution:
// MobRec.h - used as the objects in the MobInfo array
#import <Foundation/Foundation.h>
#interface MobRec : NSObject {
#public NSString *mName;
#public int mSpeed;
}
#property (nonatomic, retain) NSString *mName;
#property (nonatomic) int mSpeed;
// MobDefs.h - array of MobRecords
#interface Mobdefs : NSObject {
#public NSMutableArray *mobInfo;
}
#property(assign) NSMutableArray *mobInfo; // is this the right property?
-(void) initMobTable;
#end
// MobDefs.m
#import "Mobdefs.h"
#import "Mobrec.h"
#implementation Mobdefs
#synthesize mobInfo;
-(void) initMobTable
{
// if I use traditional method I get may not respond
[mobInfo objectAtIndex:0 setmName: #"doug"];
// if I use dot syntax I get struct has no member named mName
mobInfo[1].MName = #"eric";
}
// main.h
MobDefs *mobdef;
// main.m
mobdef = [[Mobdefs alloc] init];
[mobdef initMobTable];
although both methods should work I get erros on both. What am I doing wrong? My best thoughts have been that I am using the wrong #property but I think I have tried all. I am performing alloc in main. Ideally I would like to for this use dot syntax and cant see why its not allowing it.
A couple of things: (edit: original point #1 removed due to error)
Although the dot syntax is supported, the array index syntax for NSArray is not. Thus, your call to mobInfo[1] will not be the same as [mobInfo objectAtIndex:1]; Instead, mobInfo will be treated as a simple C-style array, and that call would be almost guaranteed to result in a crash.
You should not define variables in your header file as you do in main.h. The line MobDefs *mobdef; belongs somewhere in main.m.
edit: Here is how it should look:
MobRec.h
#interface MobRec : NSObject {
NSString *mName;
int mSpeed;
}
#property (nonatomic, retain) NSString *mName;
#property (nonatomic) int mSpeed;
MobRec.m
#implementation MobRec
#synthesize mName;
#synthesize mSpeed;
#end
MobDefs.h
#interface MobDefs : NSObject {
NSMutableArray *mobInfo;
}
#property(assign) NSMutableArray *mobInfo;
-(void) initMobTable;
#end
MobDefs.m
#import "MobDefs.h"
#import "MobRec.h"
#implementation MobDefs
#synthesize mobInfo;
-(void) initMobTable
{
// option 1:
[(MobRec*)[mobInfo objectAtIndex:0] setMName:#"doug"];
// option 2:
(MobRec*)[mobInfo objectAtIndex:0].mName = #"eric";
// option 3:
MobRec *mobRec = [mobInfo objectAtIndex:0];
mobRec.mName = #"eric";
}
main.m
MobDef *mobdef = [[MobDefs alloc] init];
[mobdef initMobTable];
...
[mobdef release]; // don't forget!
You need to either cast the object returned by -objectAtIndex:, or use a method call on it:
[[mobInfo objectAtIndex: 0] setMName: #"doug"];
or
((Mobrec *) [mobInfo objectAtIndex: 0]).MName = #"doug";
[mobInfo objectAtIndex:0 setmName: #"doug"];
There is no objectAtIndex:setmName method, so you're going to have to explain what you think this is even supposed to do.
mobInfo[1].MName = #"eric";
Use objectAtIndex to look something up in an NSArray object.
Related
I moved my app to XCode 6 and found this problem. I have NSObject and it stopped returning objects when initialized, I use XCode 6 iPhone 6 Simulator.
My .h file:
#import <Foundation/Foundation.h>
#interface RBGAlpha : NSObject{
NSString *red;
NSString *blue;
NSString *green;
NSString *alpha;
}
#property (nonatomic, retain) NSString *red;
#property (nonatomic, retain) NSString *blue;
#property (nonatomic, retain) NSString *green;
#property (nonatomic, retain) NSString *alpha;
-(id)initWithName:(NSString *)r bl:(NSString *)b gr:(NSString *)g al:(NSString *)a;
#end
my .m file
#import "RBGAlpha.h"
#implementation RBGAlpha
#synthesize red,blue,green,alpha;
-(id)initWithName:(NSString *)r bl:(NSString *)b gr:(NSString *)g al:(NSString *)a{
self = [super init];
if (self) {
self.red = r;
self.blue = b;
self.green = g;
self.alpha = a;
}
return self;
}
#end
I use something like this in viewDidLoad method to create my objects:
RBGAlpha *tmpObj=[[RBGAlpha alloc] initWithName:#"0.01" bl:#"0.01" gr:#"0.01" al:#"1.00"];
However, while running the app in Simulator iPhone 6 this returns nothing
Has anybody dealt with that kind of problem?
I think that you're being mislead. There is indeed a value, that is what 0x786... in the value field means.
Summary saying 0 objects is confusing. I cannot understand why it would say that, but I bet if you typed po tmpObj into LLDB it would not return nil but the address showing next to "Value".
If you want to see something more interesting from the Xcode debugger consider implementing debugQuickLookObject.
On a side note, you can omit the definition of your instances variables in
#interface RBGAlpha : NSObject{
NSString *red;
NSString *blue;
NSString *green;
NSString *alpha;
}
And you also don't need to #synthesize each of them anymore, the compiler included with Xcode 5 and up does this for you.
I'm working on exercise 3 on page 76 in Apple's developer pdf in the class categories and extensions section, "Programming with Objective C", found here: (https://developer.apple.com/library/mac/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html)
my XYZPerson header looks like this:
#import <Foundation/Foundation.h>
#interface XYZPerson : NSObject
#property (readonly) NSNumber *height;
#property (readonly) NSNumber *weight;
-(NSNumber *)measureHeight;
-(NSNumber *)measureWeight;
#end
My implementation file looks like this:
#import "XYZPerson.h"
#property (readwrite) NSNumber *height;
#property (readwrite) NSNumber *weight;
#end
/////////////////////
#implementation XYZPerson
-(NSNumber *)measureHeight{
if(!_height){
_height = [[NSNumber alloc] init];
}
return _height;
}
-(NSNumber *)measureWeight{
if(!_weight){
_weight = [[NSNumber alloc] init];
}
return _weight;
}
#end
And then in my main file I have:
#import <Foundation/Foundation.h>
#import "XYZPerson.h"
int main(int argc, const char * argv[])
{
#autoreleasepool {
XYZPerson *aPerson = [[XYZPerson alloc] init];
[aPerson setHeight: [NSNumber numberWithInt:72] ];
[aPerson setWeight: [NSNumber numberWithInt:190] ];
NSLog(#"%# %#",[aPerson measureHeight],[aPerson measureWeight]);
}
return 0;
}
There might be more than one error unrelated to the issue I brought up, I'm a huge novice at Objective C right now. The exact compiler error I am getting is on the line that says,
[aPerson setHeight: [NSNumber numberWithInt:72] ];
The compiler error reads, "ARC Semantic Issue. No visible #interface for 'XYZperson' declares the selector 'setWeight:'.
Oh doh.
You will not be able to call that method from OUTSIDE of your class implementation.
Overriding properties in class extensions in the .m file doesn't expose that to the world.
At least not to the compiler.
That's the whole point.
It's for when you want properties that are readonly to the world outside of that object, but internally to the object you still want to be able to conveniently do things.
You declared the property read-only in the header file, so to everything outside of the class, the properly is read-only, and thus a setHeight: method doesn't exist.
You have made he properties height and weight read only. Then in the main function you are using setWeight and setHeight.
You can't do that as that would be writing the weights but you explicitly set them to read only.
Place your properties in .m with class extension:
#interface XYZPerson ()
#property (readwrite) NSNumber *height;
#property (readwrite) NSNumber *weight;
#end
See Apple docs about class extension:
https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html
I'm new to this objective-c property attribute thing. Here's the code:
student.h
#import <Foundation/NSObject.h>
#interface Student: NSObject
#property int age(assign, readwrite); //I don't know what attribute it should have
#property NSString *name(retain, readwrite); //this one either
-(Student*) initWithName: (NSString *) n andAge:(int) a;
-(void) speakName;
+(void) smoke:(NSString*) thing;
#end
student.m
#import "student.h"
#implementation Student
-(Student*) initWithName:(NSString*) n andAge:(int) a {
self = [super init];
if(self) {
[self setName: n];
[self setAge: a];
}
return self;
}
-(void) speakName {
NSLog(#"MyName is %#", _name);
}
+(void) smoke:(NSString*) thing {
NSLog(#"Smoking %#", thing);
}
#end
main.m
#import <Foundation/Foundation.h>
#import "student.h"
int main(void) {
Student *student = [[Student alloc] initWithName: #"Markson" andAge: 29];
[student speakName];
[Student smoke:#"weed"];
[student release];
return 0;
}
for the the line
#property int age(assign, readwrite); //I don't know what attribute it should have
#property NSString *name(retain, readwrite); //this one either
when I don't give nothing to them, the compiler give me 4 warnings:
In file included from student.m:1:
./student.h:5:1: warning: no 'assign', 'retain', or 'copy' attribute is
specified - 'assign' is assumed [-Wobjc-property-no-attribute]
#property NSString *name;
^
./student.h:5:1: warning: default property attribute 'assign' not appropriate
for non-GC object [-Wobjc-property-no-attribute]
2 warnings generated.
In file included from main.m:2:
./student.h:5:1: warning: no 'assign', 'retain', or 'copy' attribute is
specified - 'assign' is assumed [-Wobjc-property-no-attribute]
#property NSString *name;
^
./student.h:5:1: warning: default property attribute 'assign' not appropriate
for non-GC object [-Wobjc-property-no-attribute]
2 warnings generated.
Please anyone can tell what attributes should be used for age and name properties?
#property int age(assign, readwrite); //I don't know what attribute it should have
#property NSString *name(retain, readwrite); //this one either
Short Note:
If you are creating property for primitive types like int, float, BOOL etc then use assign
If you want to retain the value then use strong or retain.
In all other situations you can go with weak.
And always go with atomic, and the syntax is like this
#property (<assign/retain/weak>, <atomic/nonatomic>, <read/readwrite>) <dataType> <propertyName>;
Change those lines to this:
#property (assign, nonatomic) int age;
#property (retain, nonatomic) NSString *name;
readwrite is the default one, so you don't need to set it.
Check this documentation:
Encapsulating data in Objective-C
I recently started learning Objective-C and Cocos-2D. I tried to define my own method for automating the creation of sprites.
I added my own class where I'll create other automation methods as well. Anyhow my .h file looks like this:
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#interface ActionsClass : CCNode {
}
#property (nonatomic, strong) CCSprite* createSprite;
#property (nonatomic, strong) CCSprite* spriteName;
#property (nonatomic, strong) NSString* pngName;
#property (nonatomic) CGPoint* spriteCoordinate;
- (CCSprite *)createSprite: (CCSprite *)spriteName: (NSString *)pngName: (CGPoint *)spriteCoordinate;
#end
And the .m is:
#import "ActionsClass.h"
#implementation ActionsClass
#synthesize createSprite = _createSprite;
#synthesize spriteName = _spriteName;
#synthesize pngName = _pngName;
#synthesize spriteCoordinate = _spriteCoordinate;
- (CCSprite *)createSprite: (CCSprite *)spriteName: (NSString *)pngName: (CGPoint *)spriteCoordinate
{
if (!_createSprite)
{
_createSprite = [[CCSprite alloc] init];
_spriteName = [CCSprite spriteWithFile:_pngName];
_spriteName.position = ccp(_spriteCoordinate->x, _spriteCoordinate->y);
[self addChild:_spriteName];
}
return _createSprite;
}
#end
In the main .m file where I want to call the method:
[self createSprite: saif: #"saif.png": ccp(100,100)];
This would give the warning that xcode didn't find the instance method createSprite and defaults it to id
Thanks a lot and sorry if the font or the formatting of the question aren't super neat.
Your method declaration is wrong, so you wont be able to call it.
It should be:
- (CCSprite *)createSprite:(CCSprite *)spriteName pngName:(NSString *)pngName coord:(CGPoint *)spriteCoordinate;
And called like:
[self createSprite:someSprite pngName:somePNGName coord:someCoord];
Edit: I didn't see that you were trying to call this from another class. To do that you will need to import the ActionsClass header file, and call this method on an instance of ActionsClass, e.g.
ActionsClass *actionsClassObject = [[ActionsClass alloc] init];
[actionsClassObject createSprite:someSprite pngName:somePNGName coord:someCoord];
this is a follow-up question to my last one here: iOS: Initialise object at start of application for all controllers to use .
I have set my application up as follows (ignore the DB Prefix):
DBFactoryClass // Built a DataManaging Object for later use in the app
DBDataModel // Is created by the factory, holds all data & access methods
DBViewControllerA // Will show some of the data that DBDataModel holds
moreViewControllers that will need access to the same DBDataModel Object
i will go step by step through the application, and will then in the end post the error message i get when building.
AppDelegate.h
#import "DBFactoryClass.h"
AppDelegate.m
- (BOOL)...didFinishLaunching...
{
DBFactoryClass *FACTORY = [[DBFactoryClass alloc ]init ];
return YES;
}
DBFactoryClass.h
#import <Foundation/Foundation.h>
#import "DBDataModel.h"
#interface DBFactoryClass : NSObject
#property (strong) DBDataModel *DATAMODEL;
#end
DBFactoryClass.m
#import "DBFactoryClass.h"
#implementation DBFactoryClass
#synthesize DATAMODEL;
-(id)init{
self = [super init];
[self setDATAMODEL:[[DBDataModel alloc]init ]];
return self;
}
#end
ViewControllerA.h
#import <UIKit/UIKit.h>
#import "DBDataModel.h"
#class DBDataModel;
#interface todayViewController : UIViewController
#property (strong)DBDataModel *DATAMODEL;
#property (weak, nonatomic) IBOutlet UILabel *testLabel;
#end
ViewControllerA.m
#import "todayViewController.h"
#implementation todayViewController
#synthesize testLabel;
#synthesize DATAMODEL;
- (void)viewDidLoad
{
todaySpentLabel.text = [[DATAMODEL test]stringValue];
}
#end
DBDataModel.h
#import <Foundation/Foundation.h>
#interface DBDataModel : NSObject
#property (nonatomic, retain) NSNumber* test;
#end
DBDataModel.m
#import "DBDataModel.h"
#implementation DBDataModel
#synthesize test;
-(id)init{
test = [[NSNumber alloc]initWithInt:4];
return self;
}
#end
when i build it, i get the following error: EXC_BAD_ACCESS in this line:
#synthesize DATAMODEL;
of DBFactoryClass.m
What #synthesize does is to automatically generate implementations of the accessors for a property. EXC_BAD_ACCESS there means that you're accessing garbage when one of the accessors is executed.
That's probably happening here:
[self setDATAMODEL:[[DBDataModel alloc]init ]];
Make sure that DBDataModel's implementation of init actually returns a legitimate object.
As far as I can tell, your DBFactoryClass class is never stored anywhere, and therefore released right after the allocation if you use ARC (Since you use the strong keyword I assumed you do).
- (BOOL)...didFinishLaunching... {
DBFactoryClass *FACTORY = [[DBFactoryClass alloc ]init ];
// If you use ARC this might be released right afterwards
return YES;
}
If you want the factory to be a singleton, use something like this
+ (id)sharedInstance {
static dispatch_once_t once;
static MyFoo *instance;
dispatch_once(&once, ^{
instance = [[self alloc] init];
});
return instance;
}