Naming of formal parameters in setters with synthesized properties

Question

I have been learning and using Objective-C for quite some time now (it also kind of was my first OOP language) and I finally would like to know how to correctly name synthesized properties.

Let's take the following scenario:

I have got a property called someVariable.

@property (nonatomic, retain) NSString *someVariable;

and synthesize it

@synthesize someVariable;

How would the custom setter look like conventionally ?

---

1)

I would go ahead and say something like

-(void)setSomeVariable:(NSString *)someVar{

    //input parameter MAY sound/look foreign due to the difference to the property
    someVariable = someVar;

}

---

2) (illegal)

But I would like to name the formal parameter just like the property for the sake of readability and convenience. More like in Java like this:

-(void)setSomeVariable:(NSString *)someVariable{

    //obviously illegal because this would call the setter over and over again
    self.someVariable = someVariable; 

}

---

3) (unconventional)

and according to what I have been reading in the past this

@synthesize someVariable = _someVariable; 

is said to be unconventional and not supposed to be used.

---

So, am I correct in concluding that the way I have been doing it until now, is the only way to create a custom setter ?

Answer 1

3) is not unconventional, it's exactly what the compiler does if you don't provide the @synthesize statement.

This means that, without the @synthesize statement and the ivar declaration, you have an implicit ivar named _someVariable, and a custom setter would usually have a parameter named someVariable

-(void)setSomeVariable:(NSString *)someVariable {
    _someVariable = someVariable;
}

Also note that providing custom setter and getter methods for a particular property indicates to the Xcode compiler to not provide the implicit ivar (here _someVariable). In the case of readonly properties, the same if true if you provide just the getter method.

WWDC 2012 session 405 provides a lot of details around Objective-C constructs for modern versions of the compiler.

EDIT

As H2CO3 has suggested in his answer, the code I wrote assumes you're using ARC. If you are using MRC, the setter method would rather be :

-(void)setSomeVariable:(NSString *)someVariable {
    [someVariable retain];
    [_someVariable release];
    _someVariable = someVariable;
}