In Objective c, what is the differences between instance variables var1 and var2 showing below?
(This code is in one .m file, does it make any difference if the @interface is in a header file & @implementation is in implementation file? I mean any difference comparing with that in one file regarding to the two instance variables.)
@interface MyService {
NSString *var1;
}
@end
@implementation MyService {
NSString *var2;
}
@end
The difference between them is visibility. The variable defined in the @interface section is visible to any code which imports the interface. The variable declared in the @implementation section is only visible to code within the class implementation.
If the @interface is declared in the implementation file, it will act, for all practical purposes, the same as declaring it in the @implementation section.
Instance variables declared in the implementation are implicitly hidden (effectively private) and the visibility cannot be changed - @public, @protected and @private do not produce compiler errors (with the current Clang at least) but are ignored.
you can found it here
@interface & @implementation like my code shows VS separate files, header file & implementation files), does it make any difference regarding to var1 and var 2
@public or @protected or @private, just it :).I have deep searched for your question.Well asked Leem.fin brother.I tried sample one
#import "SecondViewController.h"
@interface SecondViewController ()
{
NSString *variableOne;
}
@end
@implementation SecondViewController
{
NSString *variableTwo;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
[self setValueToString];
NSLog(@"The variable One is - %@",variableOne);
NSLog(@"The variable Two is - %@",variableTwo);
}
-(void)setValueToString
{
variableOne = @"iOS";
variableTwo = @"iPhone";
}
The printed results are
The variable One is - iOS
The variable Two is - iPhone
But when I tried to access these in Class method
+(void)changeStrings
{
variableOne = @"iPad"; //I get error here
variableTwo = @"iMac"; //I get error here
}
The error shows
Instance variable 'variableOne' accessed in class method
Instance variable 'variableTwo' accessed in class method
From above code I understood
Both are instance variables
That can be accessed only in instance methods
There is no difference between them
Difference between putting variable inside interface and implementation
