Variables of same name in different view controllers

Question

I am writing a simple tabbed iOS app. It has 3 tabs each with its own view controller. In each view controller I declare a variable of the same name:

float nitriteLevel;

But when I make a change to the value of nitriteLevel in one VC it also changes the value of nitriteLevel in the others. As I understand it, this shouldn't be, they should be completely independent & unrelated. What might I have done wrong?

How are you declaring the variable? Like this? `@property (nonatomic) float nitriteLevel;` ? — MaxGabriel, Jan 14 '13 at 23:41
I declared it as above (no *property or nonatomic) and it was declared between *interface and *implementation. Does this make it global? Just tried moving it inside @implementation and same behavior. (I thought there are no global variables in Objective-C?) — user1975122, Jan 15 '13 at 14:27

score 3 · Answer 1 · answered Jan 15 '13 at 00:09

Do you declare it in the middle of the implementation section? Or even outside any @... @end block? If so then you made it global. That is possible because beneath Objective-C there is Ansi C.

For a private instance variable do the following: MyClassName.h file:

@interface MyClassName : ItsSuperclassName <SomeProtocol> {
    float nitriteLevel;
}

// if you want it private then there is no need to declare a property. 

@end

MyClasseName.m file:

@implementation

// These days there is no need to synthesize always each property.
// They can be auto-synthesized. 
// However, it is not a property, cannot be synthesized and therefore there is no getter or setter. 

    -(void) someMehtod {

        self->nitriteLevel = 0.0f;  //This is how you access it. 
        float someValue2 = self->nitriteLevel; // That is fine. 

        self.nitriteLevel = 0.0f; // This does not even compile. 
        [self setNitriteLevel: 0.0f]; //Neither this works. 
        float someValue2 = self.nitriteLevel; // nope
        float someValue3 = [self setNitriteLevel]; // no chance

    }
@end

I am not 100% positive about the following: This type of variable is not being initialized automatically. You cannot use float nitriteLevel = 0.0f; at that point. Make sure that you initialize it in the init method. Depending on your stile initialize them latest in viewDidLoad (in View Controllers).

Variables of same name in different view controllers

1 Answers1