CODEWITHSUNDEEP
iosobjective-cenums
dev gr
dev gr

Reputation: 2431

Objective C : validity check for an enum variable

I am having a delegate function which asks for UIActivityIndicatorViewStyle from delegate.

@protocol StatusViewCustomizationDelegate <NSObject>

@optional
-(UIActivityIndicatorViewStyle)activityIndicatorStyle;

@end

Inside a private function I check if delegate responds to this selector and if it responds I call the method. Below is the code:

-(void)configureView
{
   UIActivityIndicatorViewStyle activityIndicatorStyleFromDelegate;
    if ([self.delegate respondsToSelector:@selector(activityIndicatorViewStyle)])
    {
        activityIndicatorStyleFromDelegate = [self.delegate activityIndicatorStyle];
    }
}

What is the correct way to check the enum value I received in activityIndicatorStyleFromDelegate variable is a valid UIActivityIndicatorViewStyle enum value?

Edit: UIActivityIndicatorViewStyle is an iOS defined enum.

typedef NS_ENUM(NSInteger, UIActivityIndicatorViewStyle) {
    UIActivityIndicatorViewStyleWhiteLarge,
    UIActivityIndicatorViewStyleWhite,
    UIActivityIndicatorViewStyleGray,
};

Upvotes: 2

Views: 4447

Answers (3)

Ashley Mills
Ashley Mills

Reputation: 53082

Generally, when checking enum values you're limited to one of two methods.

If the enum values are in a contiguous sequence, you can check the value is within its range:

if (activityIndicatorStyle >= UIActivityIndicatorViewStyleWhiteLarge && 
    activityIndicatorStyle <= UIActivityIndicatorViewStyleGray) {
    NSLog(@"Good");
} else {
    NSLog(@"Bad");
}

Otherwise you'll just have to test check against each value in turn:

switch (activityIndicatorStyle) {
    case UIActivityIndicatorViewStyleGray:
    case UIActivityIndicatorViewStyleWhite:
    case UIActivityIndicatorViewStyleWhiteLarge:
        NSLog(@"Good");
        break;
    default:
        NSLog(@"Bad");
}

Upvotes: 6

trojanfoe
trojanfoe

Reputation: 122381

Use this code:

if (style >= UIActivityIndicatorViewStyleWhiteLarge &&
    style <= UIActivityIndicatorViewStyleGray) {
    // valid
} else {
    // invalid
}

Upvotes: 1

Schemetrical
Schemetrical

Reputation: 5536

You can take the last value of the enum and compare if the supplied enum is less or equal than the last value of the enum, so:

- (void)configureView
{
   UIActivityIndicatorViewStyle activityIndicatorStyleFromDelegate;
    if ([self.delegate respondsToSelector:@selector(activityIndicatorViewStyle)])
    {
        if ([self.delegate activityIndicatorStyle] >= UIActivityIndicatorViewStyleWhiteLarge &&
    [self.delegate activityIndicatorStyle] <= UIActivityIndicatorViewStyleGray) {
            activityIndicatorStyleFromDelegate = [self.delegate activityIndicatorStyle];
        }
    }
}

Also, a common convention is to add one more enumeration that is called num_types and you can check if the enums are less than num_types, but this is not possible in your context.

Upvotes: 0

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