Objective-C convention to prevent "local declaration hides instance variable" warning

I am using the following code ...

-(id) initWithVariableName:(NSString*)variableName withComparisonValue:(NSString*)comparisonValue {

    // super init
    self = [super init];
    if (!self) return nil;

    // set instance variables
    self.mustExist = NO;
    self.reverseCondition = NO;
    self.regularExpression = NO;
    self.variableName = variableName; // generates warning
    self.comparisonValue = comparisonValue; // generates warning

    return self;
}

which generated the following two warnings ...

• Local declaration of 'variableName' hides instance variable
• Local declaration of 'comparisonValue' hides instance variable

Is there a common or accepted convention for dealing with these warnings?

I understand that it is simply to inform the user that they should specify an instance when referring to the class member, but its annoying.