Information in text fields do not get retained objective c - objective-c

Question

This is a simple program that takes two numbers inputed by the user in two separate text fields and adds them together when the 'Add' button is clicked. The way I have done this is by subclassing NSTextField into a class called MyTextField. I believe my error has something to do with memory leaks, but being an inexperienced programmer, I'm not quite sure how to deal with allocating and deallocating memory.
The problem is: When I click the Add button, it works perfectly. However, when I click it again, it does not show the correct amount. It keeps taking my inputs as nil and outputting 0. I have attached my code.
Note: I know that this is much more complicate than it needs to be! I am simply showing a simpler version of a much more complicated program that displays the exact same error.
MyTextField.h
#import <Cocoa/Cocoa.h>
#interface MyTextField : NSTextField
#property (strong) NSString* number;
#property double dblNum;
-(id)initWithNumber:(NSString *)number;
-(NSString *)getNumber;
-(void)setNumber;
-(double)getDblNum;
-(void)setDblNum;
-(double)calcSum:(MyTextField *)other;
-(NSString *)description;
#end
MyTextField.m
#import "MyTextField.h"
#implementation MyTextField
-(id)initWithNumber:(NSString *)number{
self = [super init];
if (self) {
if ([number length] > 0){
_number = number;
}else{
_number = #"0";
}
[self setDblNum];
}
return self;
}
- (id)init {
return [self initWithNumber:[self getNumber]];
}
-(NSString *)getNumber{
return _number;
}
-(void)setNumber{
_number = [self stringValue];
}
-(double)getDblNum{
return _dblNum;
}
-(void)setDblNum{
_dblNum = [_number doubleValue];
}
-(double)calcSum:(MyTextField *)other{
return [self getDblNum] + [other getDblNum];
}
- (NSString *)description{
return [NSString stringWithFormat: #"Number: %f", _dblNum];
}
#end
ViewController.h
#import <Cocoa/Cocoa.h>
#import "MyTextField.h"
#interface ViewController : NSViewController
#property (strong) IBOutlet MyTextField *valueOne;
#property (strong) IBOutlet MyTextField *valueTwo;
#property (strong) IBOutlet NSTextField *answer;
- (IBAction)btnAdd:(id)sender;
#end
ViewController.m
#import "ViewController.h"
#import "MyTextField.h"
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
}
- (void)setRepresentedObject:(id)representedObject {
[super setRepresentedObject:representedObject];
}
- (IBAction)btnAdd:(id)sender {
_valueOne = [[MyTextField alloc] initWithNumber:[_valueOne stringValue]];
_valueTwo = [[MyTextField alloc] initWithNumber:[_valueTwo stringValue]];
double ans = [_valueOne calcSum:_valueTwo];
_answer.stringValue = [NSString stringWithFormat:#"%.2f", ans];
}
#end
P.S. Sorry for the annoying amount of code. Thanks!

Answer 1

Your btnAdd: is where the problem is.
- (IBAction)btnAdd:(id)sender {
_valueOne = [[MyTextField alloc] initWithNumber:[_valueOne stringValue]];
_valueTwo = [[MyTextField alloc] initWithNumber:[_valueTwo stringValue]];
double ans = [_valueOne calcSum:_valueTwo];
_answer.stringValue = [NSString stringWithFormat:#"%.2f", ans];
}
Each time the button is tapped, you're recreating both MyTextField instances. Instead, you simply need to get & set the values from your existing valueOne and valueTwo outlets, like:
- (IBAction)btnAdd:(id)sender {
double value1 = [_valueOne.text doubleValue];
double value2 = [_valueTwo.text doubleValue];
double ans = value1 + value2;
_answer.stringValue = [NSString stringWithFormat:#"%.2f", ans];
}
Obviously, you need to check the validity of the valueOne and valueTwo text strings.
You really don't need a MyTextField subclass, because it's not doing anything except converting strings to doubles (and vice versa).