Question

i want to pass a variable from a viewcontroller to another the way i do is at the first viewcontroller header file i declared a variable

1.h:

NSString *string;

and at the second viewcontroller i have import the 1.h in my 2.m file,the way i call the variable is

2.m:

NSString *string2 = 1.string

however it return an error can somebody teach me how to do,because of i dont have the strong basic at Object Oriented programming ,thanks

Answer 1

Just defining and declaring the two strings is not enough. That makes sure that each class has a variable called string or string2 – but when your program is running, it is actual objects that must refer to specific instances of string1 (or string2).

It’s like designing a house with a letterbox – the letterbox is there on the plan of the house, but nothing happens until a specific letter gets sent to a specific house.

What you need to do is wire up the actual instances of your class, possibily in an init method, like this:

// 1.h  @interface ViewController1 : UIViewController { // declare our variable NSString* string1; }  // declare 'string1' as a property @property (retain) NSString* string1;  // 1.m // implements the property for string1 @synthesize string1;  // 2.h @interface ViewController2 : UIViewController { // declare our variable NSString* string2; }  // declare 'string2' as a property @property (retain) NSString* string2;  // 2.m  - (id)initWithTitle:(NSString*)aTitle andString1:aString     { if (self = [super init])     {         self.title = aTitle;         self.string1 = aString;     }  return self; } 

Then in 1.m, you create the second controller, and wire the strings up, like this:

// 1.m mySecondController = [[ViewController2 alloc] initWithTitle:@'Controller 2' andString:string1];