Issues with including Objective-C class in my xcode project - iphone

Question

I am relatively new to Objective-C, about 1 year experience, and I had encountered an issue with trying to add a class to my project. When I add a class of UIViewController subclass, with XIB file included, I have no problems with that at all, xcode is working very well that way.
However, I tried to add a simple Objective-C class to the project called Test, with the following .h and .m files, and had a problem where the code compiles and builds without error but the method TestMethod always returns nil. What might be wrong here?
Test.h
#import <Foundation/Foundation.h>
#class Test;
#interface Test : NSObject {
}
- (NSString *)TestMethod;
#end
Test.m
#import "Test.h"
#implementation Test
- (NSString*)TestMethod {
return #"Test";
}
#end
In my UIViewController subclass with XIB file, that subclass works without error, but when I try to include my Test class in it, the method TestMethod returns nothing, even though it is hardcoded to always return the same string:
#import "Test.h"
Test *testobject;
// this compiles and builds but returns nothing
NSString *testString = [testobject TestMethod];

Answer 1

You missed to alloc + init.
Use
Test *testobject=[[Test alloc] init];
or
Test *testobject=[Test new];
Whenever your object is un-initialised you will get nil value.
EDIT:
In ARC : it's default initialized .
In MRC : the value could be uninitialized (garbage value).

Answer 2

TestMethod isn't returing nil - testobject is nil.
Change
Test *testobject;
to
Test *testobject = [[Test alloc] init];

Answer 3

You have not created an instance of Test, so testObject just holds nil. You need to assign an instance of Test to the variable in order to do what you want.

Answer 4

You can also take this approach
//Test.h
#import <Foundation/Foundation.h>
#class Test;
#interface Test : NSObject {
}
- (id)init;
-(NSString*)TestMethod;
#end
Now in your Test.m file
//Test.m
#import "Test.h"
#implementation Test
- (id)init {
if (self=[super init]) {
}
return self;
}
-(NSString*)TestMethod {
return #"Test";
}
#end
Now if you want to call this Test Class in another class, you have to create an instance of Test Class.
Test *testobject = [[Test alloc] init];
NSString *testString = [testobject TestMethod];

Answer 5

To access any method/property of a class, first you need to allocate memory to object of that class using alloc/new method.
Since you created variable of that class type <Test *testobject>. But variable does not allocated any memory, by default it will be nil. Using "nil" you can call any method in objective C. It will not crash. But it will return nil.
So, Before accessing any object you must created memory for that object
Test *testobject = [Test alloc];
initialized the object with default constructor (init, initWith, etc...)
[testobject init];
Now object is ready for calling instance method/setter/getter etc...
NSString *testString = [testobject TestMethod];