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Compiler error: "initializer element is not a compile-time constant"
(7 answers)
Closed 9 years ago.
I'm trying to create a NSObject class which contains an array which contains the alphabet. When I try to implement the array, I get a warning stating that "Initializer element is not a compile-time constant" I've researched it and it has something to do with the program not knowing which value will be used at compile time I don't know how to rectify this with the code I've got. I have the interface and implementation code here:
#import <Foundation/Foundation.h>
#interface Alphabet : NSObject {
NSArray *alphabet;
}
#end
#import "Alphabet.h"
#implementation Alphabet
NSArray *alphabet = [[NSArray alloc] initWithObjects:#"a",#"b",#"c",#"d",#"e",#"f",#"g",#"h",#"i",#"j",#"k",#"l",#"m",#"n",#"o",#"p",#"q",#"r",#"s",#"t",#"u",#"v",#"w",#"x",#"y",#"z", nil];
#end
You have to initialize the objects inside a method like -(id)init. You can declare the objects under #implementation like:
#implementation Alphabet
{
NSArray *alphabet;
}
- (id)init
{
self = [super init];
if (self)
{
NSLog(#"init");
NSArray *alphabet = [[NSArray alloc] initWithObjects:#"a",#"b",#"c",#"d",#"e",#"f",#"g",#"h",#"i",#"j",#"k",#"l",#"m",#"n",#"o",#"p",#"q",#"r",#"s",#"t",#"u",#"v",#"w",#"x",#"y",#"z", nil];
}
return self;
}
#end
If you initialize an object outside of a method, that object's value needs to be written into the executable file. So you can only use a constant value in that case. You can't create any Objective-C objects except constants until runtime.
You can make the array a property and initialize it "lazily":
#interface Alphabet : NSObject
#property (nonatomic, strong) alphabet;
#end
#import "Alphabet.h"
#implementation Alphabet {
NSArray* _alphabet;
}
#synthesize alphabet = _alphabet;
// getter
- (NSArray*) alphabet {
if (_alphabet == nil) {
_alphabet = #[#"a",#"b",#"c",#"d",#"e",#"f",#"g",#"h",#"i",#"j",#"k",#"l",#"m",#"n",#"o",#"p",#"q",#"r",#"s",#"t",#"u",#"v",#"w",#"x",#"y",#"z"];
}
return _alphabet;
}
#end
Note:
The statement
_alphabet = #[#"a",#"b",#"c", ..., #"z"];
is a short hand for
_alphabet = [[NSArray alloc] initWithObjects:#"a",#"b",#"c", ..., #"z", nil];
Related
I'm very new to objective-c so be easy :-) I have a container object, "Data", who has a number of NSMutableArrays.
Data.h
#interface Data : NSObject{
NSMutableArray *one;
NSMutableArray *two;
}
#property (nonatomic, retain) NSMutableArray *one;
#end
and would like to pass it to a load method in which case it will update each corresponding array in the Data class.
Parser.h
+ (Parser *)load:(Data*) store;
Parser.m
+ (Parser *)load:(Data *) store {
...
[store.one addObject:name.stringValue];
}
But no matter what I do the string in "name.stringValue" doesn't get appended to the array. Is there something I'm missing when passing in the "Store" data object to the parse method? Let me know if I should provide more details but I feel this covers the issue.
Check in your implementation of Data that you are properly initializing the mutable arrays - here is a simple example below given your Data interface:
#import "Data.h"
#implementation Data
{
#pragma mark - Properties
- (NSMutableArray *)one
{
if (!_one) {
_one = [[NSMutableArray alloc] init];
}
return _one;
}
- (NSMutableArray *)two
{
if (!_two) {
_two = [[NSMutableArray alloc] init];
}
return _two;
}
}
Use one = [NSMutableArray array]; before you start using it. This will create an empty mutable array.
Using Objective-C, is it possible to go through an array by groups :
exemple :
NSArray *arr = 1, 2, 3, ....100;
Every 10 objects, do something and go on
so :
object 0 to 9 : you do something with each object and after the 10° object you do a last action
then object 10 to 19 : you do something with each object and after the 19° object you do a last action
and so on until the last object
thank you for your help
something like this:
for (int i = 0; i < arr.count; i++)
{
[self doSomethingWithArray];
if (i % 10 == 0)
[self doSomethingElse];
}
No it is not possible in Objective-C with in-built functions which matches your exact description. There are crude ways to do it by loops which matches your exact description.
But if you are aware before hand that you are going to make such type of operations, define your own data-structure. Create an NSObject sub-class, define your items (10 items which you were talking about) in it. Then in array, you can directly take out each instance of it comprising of your defined NSObject.
"enumerating by group"; If you want exactly as stated, you can subclass NSEnumerator.
For example:
In your Application code:
#import "NSArray+SubarrayEnumerator.h"
NSArray *arr = ...;
for(NSArray *grp in [arr subarrayEnumeratorEach:10]) {
// do what you want.
}
NSArray+SubarrayEnumerator.h
#import <Foundation/Foundation.h>
#interface NSArray (SubarrayEnumerator)
- (NSEnumerator *)subarrayEnumeratorEach:(NSUInteger)perPage;
#end
NSArray+SubarrayEnumerator.m
#import "NSArray+SubarrayEnumerator.h"
#interface _NSArraySubarrayEnumeratorEach : NSEnumerator
#property (assign, nonatomic) NSUInteger cursor;
#property (assign, nonatomic) NSUInteger perPage;
#property (strong, nonatomic) NSArray *src;
#end
#implementation NSArray (SubarrayEnumerator)
- (NSEnumerator *)subarrayEnumeratorEach:(NSUInteger)perPage {
_NSArraySubarrayEnumeratorEach *enumerator = [[_NSArraySubarrayEnumeratorEach alloc] init];
enumerator.perPage = perPage;
enumerator.src = self;
return enumerator;
}
#end
#implementation _NSArraySubarrayEnumeratorEach
- (id)nextObject {
NSUInteger start = _cursor;
if(start >= _src.count) {
return nil;
}
NSUInteger count = MIN(_perPage, _src.count - start);
_cursor += _perPage;
return [_src subarrayWithRange:NSMakeRange(start, count)];
}
#end
I'm new to iphone app development and I'm stuck on this problem I'm having with the app I'm trying to develop.
I have a datacontroller for populating a tableview. I created it using this tutorial:
About Creating Your Second iOS App
I'm trying to pass an array from one of my viewcontrollers that was created from a JSON response.
Here is some code from my viewcontroller.h that needs to pass the array:
#interface ViewController : UIViewController
#property (nonatomic, retain) DataController *Data;
#property (nonatomic, retain) NSMutableArray *array;
#end
viewcontroller.m:
#import "DataController.h"
[Data setMasterList: self.array];
DataController.h:
#interface DataController : NSObject
#property (nonatomic, strong) NSMutableArray *masterList;
- (void)setMasterList:(NSMutableArray *)newList;
#end
DataController.m
#import "LoginViewController.h"
- (void)setMasterList:(NSMutableArray *)newList {
if (_masterList != newList) {
_masterList = [newList mutableCopy];
NSLog("List: %#", newList);
}
}
The NSLog message never shows up in the console and the array is nil.
Any help is appreciated.
Thanks.
EDIT:
Here's the updated viewcontroller.m:
Data = [[DataController alloc] init];
[Data setMasterList: self.array];
The datacontroller.m:
- (void)setMasterList:(NSMutableArray *)newList {
if (_masterList != newList) {
_masterList = [newList mutableCopy];
NSLog("List: %#", self.masterList);
}
}
- (NSUInteger)countOfList {
NSLog("List: %#", self.masterList);
return [self.masterList count];
}
The first nslog inside setMasterList returns the correct array values, but the second nslog inside countOfList returns null. The list always returns null anywhere outside of setMasterList. Is it because I'm creating a new instance of the DataController? If so, how else could I pass the array to the datacontroller.
As in first comment Till have suggested, Data must be initialized before calling setMasterList. Such As:
Data = [[DataController alloc] init];
[Data setMasterList: self.array];
please help me to solve a simple problem.
I am a beginner in objective-c, and I am just switched to objective-c from java. I know java fair well, but not quite super deep into it.
I am building a iphone app. My app is quite simple.
The purpose of my iphone app is to take order with my iphone app in a restaurant.
Progress of My App:
My app only has couple viewPanels and buttons now :)
Here is my app sourcecode, firstview screenshot & secondview screenshot
Problem:
When i click on the Coffee button, my textField wont show up the coffee name & coffee price, which suppose to show up " coffee 1" .
and xcode will take me to the debugger from the iphone similator.(i think its crush at a line so the dubugger took me to the IBaction method and break at the line #synthesize name; It compiles with no error. please help trouble shoot why xcode take me to debugger when i press the coffee button.
SCREEN SHOWS UP RIGHT AFTER PRESS THE COFFEE BUTTON
here is the action code of the coffee button
- (IBAction)Coffee:(id)sender {
int price = 1;
NSString *name = #"coffee";
Storage *order = [[Storage alloc] init];
[order setName:name]; // i assume the program crush at here when it look into setName method.
[order setPrice:price];
[orders addOrders:order];
// Sanity check: // the program not even hit this line yet before crush;
NSLog(#"There are now %d orders in the array.", [orders.getOrders count]);
for (Storage *obj in orders.getOrders){
[check setText:[NSString stringWithFormat:#"%#",[obj description]]]; // check is the TextField instant varible. and the description method is from storage.m to print out the name and price.
}
}
The codes below are my storage classes that store all items that my customer orders.
it is a 2 dimensional array, and My Storages class is a wrapper class of Storage class.
the array format looks like this:
arrayindex1-> name, price
arrayindex2-> name, price
arrayindex3-> name, price
arrayindex4-> name, price
Storage.h
#import <Foundation/Foundation.h>
#interface Storage : NSObject
#property (nonatomic, strong) NSString *name;
#property (nonatomic, assign) NSInteger price;
#end
Storage.m
#import "Storage.h"
#implementation Storage
#synthesize name; // program crush and goes to here.
#synthesize price;
- (NSString *)description {
// example: "coffee 1"
return [NSString stringWithFormat:#"%# %d", self.name, self.price];
}
#end
Storages.h
#import <Foundation/Foundation.h>
#import "Storage.h"
#interface Storages : NSObject
#property (nonatomic,strong, readwrite) NSMutableArray *orders;
-(void) addOrders:(Storage *)anOrder;
-(NSMutableArray *) getOrders;
#end
Storages.m
#import "Storages.h"
#implementation Storages
#synthesize orders;
- (id)init {
self = [super init];
if (self) {
orders = [[NSMutableArray alloc] init];
}
return self;
}
-(void) addOrders:(Storage *)anOrder{
[orders addObject: anOrder];
}
-(NSMutableArray *) getOrders{
return orders;
}
#end
There are a couple of problems here.
1) Don't use a pointer for the price property. Generally, unless you're doing something unusual, your properties that are objects will be pointers and your properties that are primitives (NSInteger, BOOL, float, etc) will not be pointers.
2) You will want to make sure that the orders NSMutableArray is initialized with the Storages object, otherwise orders will remain nil and whenever you try to add objects to it, nothing will happen. To initialize the NSMutableArray, do this in your init method as shown below. You can also check that the object is actually getting into a valid mutable array this by putting a simple NSLog statement in the for (Storage *obj in orders.getOrders) { ... } loop and making sure you get at least one iteration through the loop. If orders.getOrders is nil, the work block of the for loop will never get run.
3) It sounds like you need to override (and may have already overridden) the -[NSObject description]method for your Storage object. My guess is you have a mismatch in this method with the -[NSString stringWithFormat:...] format string. For example, you might be using %d or %# in the format string for the NSInteger *. Something like that could definitely cause a crash (which is what I think you mean by "Xcode taking you to the debugger"). For NSIntegers you need to use %d or %i. And as myself and others have mentioned, you want NSInteger here and not NSInteger * and you should change your property declaration.
4) Based on what you have here, I don't think you need the order property in the Storages class at all.
5) Make sure you haven't overlooked the possibility of forgetting to hook up the IBOutlet in Interface Builder to the check textField. A good test for this, besides just confirming it's connected in Interface Builder, would be a reality check test like [check setText:#"This is a test."];
6) Keep in mind that once this works, your for loop is going to execute very quickly, and you'll immediately see only the description for the last object in the orders array. But that doesn't seem to be what your question is about.
I'd suggest you make the following changes:
Storage.h
#import <Foundation/Foundation.h>
#interface Storage : NSObject
#property (nonatomic, strong) NSString *name;
#property (nonatomic, assign) NSInteger price;
#end
Storage.m
#import "Storage.h"
#implementation Storage
#synthesize name;
#synthesize price;
- (NSString *)description {
// example: "coffee 1"
return [NSString stringWithFormat:#"%# %d", self.name, self.price];
}
#end
Your IBAction method
- (IBAction)Coffee:(id)sender {
int price = 1;
NSString *name = #"coffee";
Storage *order = [[Storage alloc] init];
[order setName:name];
[order setPrice:price];
[orders addOrders:order];
// Sanity check:
NSLog(#"There are now %d orders in the array.", [orders.getOrders count]);
for (Storage *obj in orders.getOrders){
[check setText:[NSString stringWithFormat:#"%#",[obj description]]]; // check is the TextField instant varible. and the description method is from storage.m to print out the name and price.
}
}
Storages.h
#import <Foundation/Foundation.h>
#import "Storage.h"
#interface Storages : NSObject
#property (nonatomic,strong, readwrite) NSMutableArray *orders;
-(void) addOrders:(Storage *)anOrder;
-(NSMutableArray *) getOrders;
#end
Storages.m
#import "Storages.h"
#implementation Storages
#synthesize orders;
- (id)init {
self = [super init];
if (self) {
orders = [[NSMutableArray alloc] init];
}
return self;
}
-(void) addOrders:(Storage *)anOrder{
[orders addObject: anOrder];
}
-(NSMutableArray *) getOrders{
return orders;
}
#end
What does description do in the following? (I cannot see any description object in Storage class):
[check setText:[NSString stringWithFormat:#"%#",[obj description]]];
I think if you want to print the name the do like:
[check setText:[NSString stringWithFormat:#"%#: %#",obj.name, obj.price]];
You have taken NSInteger pointer in Storages class which is not correct. NSInteger is basic data type and not a pointer. Remove that pointer and use NSInteger variable.
I hope this would resolve your problem.
You could use below code:
#interface Storage : NSObject
#property (nonatomic, retain)NSString *name;
#property (nonatomic, assign)NSInteger price;
You have two mistakes:
1- You declared price as an NSInteger and passed it as a reference. The correct is to pass it as an integer as it is and deal with it as an integer through the whole application.
2- You didn't initialize orders array in Storages class so it will be always nil and will not hold any added object.
You code may looks like:
In the button's IBAction pass the price directly
[order setPrice:price];
In the Storage class
- (NSString *)description {
return [NSString stringWithFormat: #"%# %d", name, price];
}
Add the following to the Storages class
-(id)init
{
if (self = [super init])
{
orders = [[NSMutableArray alloc] init];
}
return self;
}
The goal, to create a class which contains an array of data to be used throughout the application by other classes.
I have this GlobalObject.h
It declares the array to be used to store the data.
#import <Foundation/Foundation.h>
#interface GlobalObjects : NSObject
#property (retain) NSMutableArray *animals;
-(id)init;
#end
I have this GlobalObject.m.
It contains the NSDictionary data and stores in to the array.
#import <Foundation/Foundation.h>
#interface GlobalObjects : NSObject
#property (retain) NSMutableArray *animals;
-(id)init;
#end
#import "GlobalObjects.h"
#implementation GlobalObjects
#synthesize animals;
-(id)init{
self = [super init];
if (self) {
// Define the data
NSArray *imagesValue = [[[NSArray alloc] initWithObjects:#"dog.wav",#"cat.png",#"bird.png",nil] autorelease];
NSArray *audioValue =[[[NSArray alloc] initWithObjects:#"dog.wav",#"cat.wav",#"bird.wav",nil] autorelease];
NSArray *descriptionValue = [[[NSArray alloc] initWithObjects:#"Dog",#"Cat",#"Bird",nil] autorelease];
// Store to array
for (int i=0; i<8; i++) {
NSDictionary *tempArr = [NSDictionary dictionaryWithObjectsAndKeys:[imagesValue objectAtIndex:i],#"image", [audioValue objectAtIndex:i],#"audio", [descriptionValue objectAtIndex:i], #"description", nil];
[self.animals addObject:tempArr];
}
}
return self;
}
#end
Here's how I call it.
// someOtherClass.h
#import "GlobalObjects.h"
#property (nonatomic, retain) GlobalObjects *animalsData;
// someOtherClass.m
#synthesize animalsData;
self.animalsData = [[[GlobalObjects alloc] init] autorelease];
NSLog(#"Global Object %# ",self.animalsData.animals);
Now the problem is, when I call this array in another class, it always returns null.
I'm new to iOS programming. So probably my method is wrong?
You forgot to allocate the animals array in the init method of "GlobalObjects":
self.animals = [[NSMutableArray alloc] init];
If you don't do this, self.animals is nil and addObject has no effect.
Since you do not use ARC, remember to release the array in dealloc.
EDIT: As #H2CO3 and #Bastian have noticed, I forgot my pre-ARC lessons. So the correct way to allocate self.animals in your init method is
self.animals = [[[NSMutableArray alloc] init] autorelease];
and in dealloc you have to add
self.animals = nil;
before calling [super dealloc]. I hope that I got it right now!
Yes, it's wrong - an instance variable isn't tied to a class itself, but to a particular instance of the class. The Cocoa-standard solution to this problem is creating a shared instance of the class - instead of
elf.animalsData = [[[GlobalObjects alloc] init] autorelease];
write
elf.animalsData = [GlobalObjects sharedInstance];
and implement the + sharedInstance method like this:
+ (id)sharedInstance
{
static shared = nil;
if (shared == nil)
shared = [[self alloc] init];
return shared;
}
As #MartinR pointed out, you make another mistake: you don't create the array you're adding objects to - then it remains nil, cancelling out the effect of all method calls on itself. You have to alloc-init a mutable array for it in the - init method.