Objective-C, set and get variables in class object which is stored in NSArray

Question

I am trying to write my own class storing data about libraries and then store each object in an NSArray.

My interface:

#import <Foundation/Foundation.h>

@interface LibraryInfo : NSObject
{

NSString* name;
NSString* address;
NSString* link;
NSString* coordinates;

}

- (NSString*) getName;
- (NSString*) getAddress;
- (NSString*) getLink;
- (NSString*) getCoordinates;

- (void) setName: (NSString*)input;
- (void) setAddress: (NSString*)input;
- (void) setLink: (NSString*)input;
- (void) setCoordinates: (NSString*)input;

@end

My implementation:

#import "LibraryInfo.h"

@implementation LibraryInfo

- (void) setName: (NSString*)input
{
name = input;
}

- (void) setAddress: (NSString*)input
{
address = input;
}

- (void) setLink: (NSString*)input
{
link = input;
}

- (void) setCoordinates: (NSString*)input
{
coordinates = input;
}

- (NSString*) getName {
return name;
}

- (NSString*) getAddress {
return address;
}

- (NSString*) getLink {
return link;
}

- (NSString*) getCoordinates {
return coordinates;
}

@end

I write and store each object in the NSArray, like so:

LibraryInfo *library = [[LibraryInfo alloc] init];
[library setName:( ( name != nil && name.length > 0 ) ? name : @"No Name" )];
[library setAddress:( ( address != nil && address.length > 0 ) ? address : @"No Address" )];
[library setLink:( ( link != nil && link.length > 0 ) ? link : @"No Link" )];
[library setCoordinates:( ( coordinate != nil && coordinate.length > 0 ) ? coordinate : @"No Coordinates" )];
    
[libraries addObject: library];

Where 'libraries' is an NSArray.

Then I try to read the values like so:

cell.textLabel.text = [[ libraries objectAtIndex:indexPath.row ] getName ];
cell.detailTextLabel.text = [[ libraries objectAtIndex:indexPath.row ] getAddress ];

I think it may be something to do with the setting of the values, or maybe they are not properly stored or retained, but I get the following error and a marker by my 'setName' method
when the App 'crashes' and pauses:

self    LibraryInfo *const  0x068a1760
input   NSString *  0x068a3550
name    NSString *  0x00000000

How do I fix this? I'm using Xcode 4.3 so no releases/retains needed.

Answer 1

You need to declare properties. IVars aren't going to store your data the way you're expecting

LibraryInfo.h

@interface LibraryInfo : NSObject

@property (nonatomic, strong) NSString* name;
@property (nonatomic, strong) NSString* address;
@property (nonatomic, strong) NSString* link;
@property (nonatomic, strong) NSString* coordinates;

LibraryInfo.m

@implementation LibraryInfo
@synthesize name;
@synthesize address;
@synthesize link;
@synthesize coordinates;

Then creating libraries would be simple

LibraryInfo *library = [[LibraryInfo alloc] init];
library.name = (name.length > 0 ? name : @"No Name");
library.address = (address.length > 0 ? address : @"No Address")
library.link = (link.length > 0 ? link : @"No Link")
library.coordinates = (coordinates.length > 0 ? coordinates : @"No Coordinates")

Then in your TableView cell.

cell.textLabel.text = [libraries objectAtIndex:indexPath.row].name;
cell.detailTextLabel.text = [libraries objectAtIndex:indexPath.row].address;