Use of Undeclared Identifier 'calculateAge' [closed] - objective-c

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Closed 10 years ago.
I am new to objective and just trying to understand simple concepts.
I have read Objective C for dummies and Cocoa Programming for Mac OSX (most of it).
I tried to make a simple small program on my own and realized I know very little.
I keep getting the "Use of Undeclared Identifier "calculateAge', did you mean 'Calculate' " error.
Can anyone please tell me what's wrong with my code below and why?
Thanks a bunch in advance.
#import <Foundation/Foundation.h>
#interface Calculate : NSObject
{
int myYear;
int nowYear;
}
- (int) calculateAge:(int)birthYear:(int)nowYear;
#end
#implementation Calculate
- (int) calculateAge:(int)birthYear:(int)nowYear// need myYear
{
NSLog(#"The birthYear is: %i\n", birthYear);
int myAge = nowYear - birthYear;
//NSLog(#"The nowYear is: %i\n", nowYear);
NSLog(#"The age is: %i\n", myAge);
return myAge;
}
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSLog(#"Hello, World!");
int myY = 1963;
int nowY = 2012;
int myYear = 1963;
int nowYear = 2012;
//int myAge = calculateAge:(int) birthYear: (int) nowYear;
int myAge = calculateAge:(int) myY: (int) nowY;
NSLog(#"The nowYear is: %i\n", nowYear);
NSLog(#"The age is: %i\n", myAge);
}
return 0;
}
#end

Answer 1

You seem to be conflating the method name with the parameter list. A proper signature would look something like this:
- (int)calculateAgeFromBirthYear:(int)birthYear currentYear:(int)currentYear
This could then be implemented like this:
- (int)calculateAgeFromBirthYear:(int)birthYear currentYear:(int)currentYear
{
NSLog(#"The birthYear is: %i\n", birthYear);
int myAge = currentYear - birthYear;
//NSLog(#"The nowYear is: %i\n", currentYear);
NSLog(#"The age is: %i\n", myAge);
return myAge;
}
This could then be called like this:
Calculate *calculator = [[Calculate alloc] init];
int myAge = [calculator calculateAgeFromBirthYear:myY currentYear:nowY];
Don't implement main inside a class implementation; it belongs outside in the global namespace, preferably in its own file.

Answer 2

There is no need to declare the instance variables in the interface.
The last #end needs to be before the main function, it is not part of the class, it used the class.
The Calculate class needs to be instantiated and the call needs to be made to the instantiated class.
The calculateAge... method should be renamed to indicate each argument.
Variables should be given full names, abreviations generall end up making things less clear.
Here is an example:
#interface Calculate : NSObject
- (int) calculateAgeWithBirthYear:(int)birthYear nowYear:(int)nowYear;
#end
#implementation Calculate
- (int) calculateAgeWithBirthYear:(int)birthYear nowYear:(int)nowYear// need myYear
{
NSLog(#"The birthYear is: %i\n", birthYear);
int myAge = nowYear - birthYear;
NSLog(#"The age is: %i\n", myAge);
return myAge;
}
#end
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSLog(#"Hello, World!");
int myBirthYear = 1963;
int nowYear = 2012;
Calculate *calculator = [[Calculate alloc] init];
int myAge = [calculator calculateAgeWithBirthYear:myBirthYear nowYear:nowYear];
NSLog(#"The nowYear is: %i\n", nowYear);
NSLog(#"The age is: %i\n", myAge);
}
return 0;
}
NSLog output:
Hello, World!
The birthYear is: 1963
The age is: 49
The nowYear is: 2012
The age is: 49
Using instance variables created by `#property~ statements:
#interface Calculate : NSObject
#property int myYear;
#property int nowYear;
- (int) calculateAge;
#end
#implementation Calculate
- (int) calculateAge // need myYear
{
NSLog(#"The birthYear is: %i\n", self.myYear);
int myAge = self.nowYear - self.myYear;
NSLog(#"The age is: %i\n", myAge);
return myAge;
}
#end
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSLog(#"Hello, World!");
Calculate *calculator = [[Calculate alloc] init];
calculator.myYear = 1963;
calculator.nowYear = 2012;
int myAge = [calculator calculateAge];
NSLog(#"The nowYear is: %i\n", calculator.nowYear);
NSLog(#"The age is: %i\n", myAge);
}
return 0;
}