I am trying to make a conversion calculator with Xcode - ios

Question

I have made the basic build and it includes a picker. So whatever units of conversion the user selects from the picker, the labels should be updated to show the names of the units for that conversion and once the user enters the number in the text box and hits the button, the answer should be displayed in the second text box. Now the code executes, but the problem is no matter what I pick in the picker, it always does the weight conversion. I know I need a switch statement in there, but I'm not sure how or where I need to implement it.
Another problem is that the labels update, but only when the "Convert" button is pressed, so please help me fix this.
This is my ViewController.h file
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
<UIPickerViewDelegate, UIPickerViewDataSource> {
IBOutlet UITextField *field1;
IBOutlet UITextField *field2;
IBOutlet UIPickerView *picker;
IBOutlet UILabel *label1;
IBOutlet UILabel *label2;
}
#property (weak, nonatomic) IBOutlet UILabel *textLabelData1;
#property (weak, nonatomic) IBOutlet UILabel *textLabelData2;
#property (nonatomic, retain) UIPickerView *picker;
-(IBAction) currencyConvert:(id)sender;
-(IBAction) weightConvert:(id)sender;
-(IBAction) distanceConvert:(id)sender;
#end
This is my ViewController.m file
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize picker;
static NSString *pd[3] = {#"Currency", #"Weight", #"Speed"};
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark UIPickerViewDelegate & UIPickerViewDataSource methods
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return 1;
}
-(NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component
{
return 3;
}
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:
(NSInteger)row forComponent:(NSInteger)component;
{
return pd[row];
}
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:
(NSInteger)row inComponent:(NSInteger)component
{
NSLog(#"didSelectRow %li, inComponent: %li", row, component);
}
-(IBAction)currencyConvert:(id)sender
{
if (pd[0])
{
self.textLabelData1.text = #"Dollar";
self.textLabelData2.text = #"Rupees";
float dollar = [[field1 text] floatValue];
float rupees = dollar * 64.15;
[field2 setText: [NSString stringWithFormat: #"%3.3f", rupees]];
}
/* self.textLabelData1.text = #"Dollar";
self.textLabelData2.text = #"Rupees";
float dollar = [[field1 text] floatValue];
float rupees = dollar * 64.15;
[field2 setText: [NSString stringWithFormat: #"%3.3f", rupees]]; */
}
-(IBAction)weightConvert:(id)sender
{
if (pd[1])
{
self.textLabelData1.text = #"Kilogram";
self.textLabelData2.text = #"Lbs";
float kilogram = [[field1 text] floatValue];
float pounds = kilogram * 2.20462;
[field2 setText: [NSString stringWithFormat: #"%3.3f", pounds]];
}
}
-(IBAction)distanceConvert:(id)sender
{
if (pd[2])
{
self.textLabelData1.text = #"Mile";
self.textLabelData2.text = #"Kilometer";
float miles = [[field1 text] floatValue];
float kilometers = miles * 1.60934;
[field2 setText: [NSString stringWithFormat: #"%3.3f", kilometers]];
}
}
/* Pseudocode for switch statement
-- I tried doing this here, but it gives me an
error saying that "row" is undefined. I understand that
it is a local variable, but how else would I write the
switch statement?
Also, is the placement of the switch statement appropriate here
or will I need to implement it in a function?
switch (row)
{
case 1:
call currencyConvert
case2:
call weightConvert
case3:
call distanceConvert
}
*/
The link to the picture of my Main.storyboard

Answer 1

This isn't the ideal UI and creates inefficiencies, but its your app. I just wanted to point out that you might want to spend time working on its design and structure.
As for a solution to your problem, I cant fix everything for you, but I'll point out some things to make it easier for you.
The reason your labels are not updating is because you are not updating anything until you hit the convert button. The below function is where you'll get the event for the picker's new row
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:
(NSInteger)row inComponent:(NSInteger)component
{
NSLog(#"didSelectRow %li, inComponent: %li", row, component);
}
Try this instead:
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:
(NSInteger)row inComponent:(NSInteger)component
{
NSLog(#"didSelectRow %li, inComponent: %li", row, component);
switch (row) {
case 0:
self.textLabelData1.text = #"Dollar";
self.textLabelData2.text = #"Rupees";
break;
case 1:
// and so on
}
}
Your next issue is that you're not telling your "convert" functions what row is currently selected, and your conditional if does nothing.
In obj-c conditional statements used directly on a variable are basically just checks for initialization. if(x) simply means has x been initialized as a variable = true, if not = false. That's probably not the logic you're looking for in this case.
Next, It appears you're trying to link 3 different functions to the same button press? This is where your above if related issue is causing problems, all three functions are firing at the same time... but only one gets the last say. Presumably the one you linked last, though i cant say for sure. I'd suggest a single function that handles the button press and then relays to the correct methods.
Last, you're never telling the functions anything about the state of the picker. You need to set it as an IBOutlet so your variables will have access to it. Then you can use the picker's selected row function to determine which conversion to use.
The things I highlighted will fix your problems, BUT I would highly recommend checking out some tutorials so you'll learn more about why things do what. I'd recommend: https://www.raywenderlich.com/
Hope that helps!