CODEWITHSUNDEEP
objective-c
DaveR
DaveR

Reputation: 1425

Static variables in objective-C

I've searched through the posts about static variables in Objective-C but haven't quite found an answer to this question:

In Java, I can create a class with static variables of the same class type, like this:

public class Status {

    public static final Status SUCCESS = new Status(0, "Success");
    public static final Status FAILURE = new Status(-1, "It's Broke");

    private int number;
    private String message;

    private Status(int number, String message) {
        this.number = number;
        this.message = message;
    }
}

And then I can use the static variables in Status like this:

public Status foo() {
    ...
    return Status.FAILURE;
}

Could someone tell me how I would do something similar in Objective-C?

Upvotes: 0

Views: 328

Answers (1)

DrummerB
DrummerB

Reputation: 40201

Most of the Cocoa APIs use simple enums to return such results.

typedef enum {
    MyClassResultSuccess = 0,
    MyClassResultFailure = -1
} MyClassResult;

If you want to use a more similar approach to what you posted, you could use class methods:

@interface Status
@property (nonatomic) int value;
@property (nonatomic, copy) NSString *message;
- (id)initWithValue:(int)value message:(NSString *)message;
+ (Status *)success;
+ (Status *)failure;
@end

@implementation Status

static Status *_success = nil;
static Status *_failure = nil;

- (id)initWithValue:(int)value message:(NSString *)message {
    self = [super init];
    if (self) {
        self.value = value;
        self.message = message;
    }
    return self;
}

+ (Status *)success {
    if (!_success)
        _success = [[Status alloc] initWithValue:0 message:@"Success"];
    return _success;
}

+ (Status *)failure {
     if (!_failure)
        _failure = [[Status alloc] initWithValue:-1 message:@"Failure"];
    return _failure;
}

@end

Upvotes: 1

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