macOS Access elements of Test**

[amalshah71]

say for eg i have :

Test.h

@interface Test : NSObject
{
    @public
    NSString* temp;
}
-(id)init;
-(NSString*)giveMeRandomString;
@end

Test.m

@implementation Test

-(id)init
{
   temp=@"temp";
   return self;
}

-(NSString*)giveMeRandomString
{
    return @"random";
}

@end

AnotherClass.m

@implementation AnotherClass

-(void)access
{
      Test* t=[[Test alloc] init];
      
      NSLog(t->temp); // ok

      NSLog([t giveMeRandomString]); // ok

      Test** tt=&t;

      NSLog(tt->temp); // why such a access is permissible

      NSLog(*tt->temp); // ok...should be this way and not like the above step

      NSLog([tt giveMeRandomString]); // compiler error...alright

      NSLog([*tt giveMeRandomString]); // ok
}

@end

So, why does < NSLog(tt->temp) > work?

Or is there something i am missing...


Thanks
amal

 

[amalshah71]

Guys...pls help....am not able to understand why such a behaviour is possible....in objective-c...or is it that there is something i am missing...

amal

 

[kainjow]

It doesn't work for me on Xcode 3.1.3. I get "error: request for member 'temp' in something not a structure or union"

 

[amalshah71]

It doesn't work for me on Xcode 3.1.3. I get "error: request for member 'temp' in something not a structure or union"

Sorry....i didn't include @property statement in Test file

Test.h

@interface Test : NSObject
{
    @public
    NSString* temp;
}
@property(nonatomic)NSString* temp;
-(id)init;
-(NSString*)giveMeRandomString;
@end

Test.m

@implementation Test

@synthesize temp;

-(id)init
{
   temp=@"temp";
   return self;
}

-(NSString*)giveMeRandomString
{
    return @"random";
}

@end

amal

 

[hazmatzak]

If you consider that P->ivar is equivalent to (*P).ivar

because you declared a @property temp, which enables the dot operator

then your tt->temp is actually (*tt).temp

which does work, through property access. You can see this in a couple of ways. First, as you saw yourself, the code did not compile without declaring the property.

If you invoke the Xcode completion list with the cursor inside "temp" for t->temp, it tells you that the type is "Test" and that "temp" is a variable (with the "V" icon). If you do it in tt->temp, the type is "Test *" and "temp" is a property (with the "P" icon) -- the same as if you do it in t.temp.

Finally you can verify that the accessor is being called by defining one that returns something different than the instance variable.

Also, because of operator precedence, instead of *tt->temp, what you really mean is (*tt)->temp -- which accesses the public ivar.