Question

I implemented a simple UIPickerView in my app and I keep getting warnings that I can’t explain about incomplete implementation and “method in protocol not completed”. I went through a bunch of examples and could not figure out what am I missing.

Here is my code:

.h

@interface ViewTestViewController : UIViewController <UITableViewDelegate, UITableViewDataSource, UIPageViewControllerDataSource, UIPageViewControllerDataSource> {

 UIPickerView *pickerView;
NSMutableArray *pickerList;

....

}
@property (nonatomic, retain) IBOutlet UIPickerView *pickerView;
@property (nonatomic, retain) NSMutableArray *pickerList;


@end

.m

- (void)viewDidLoad
{
[super viewDidLoad];

 …

//PICKER AREA
pickerList = [[NSMutableArray alloc] init];
[pickerList addObject:@"aaa"];
[pickerList addObject:@"bbb"];

CGRect pickerFrame = CGRectMake(0, 200, 0, 0);
pickerView = [[UIPickerView alloc] initWithFrame:pickerFrame];
pickerView.showsSelectionIndicator = YES;    

}

-(IBAction)showPicker:(id)sender {

 [self.view addSubview:pickerView];

}

-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView
{
return 1;
}

-(NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component
 {
return [pickerList count];
}

-(NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return [pickerList objectAtIndex:row];
}

-(void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
NSLog(@"Selected item: %@ index of selected item: %i", [pickerList objectAtIndex:row], row);
}

- (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component
{

return 200;
}

Answer 1

You need to conform to the UIPickerViewDelegate and UIPickerViewDataSource in your .h like you do for UITableViewDelegate, UITableViewDataSource etc (you’re currently not)

@interface ViewTestViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate, UITableViewDelegate, UITableViewDataSource, UIPageViewControllerDataSource, UIPageViewControllerDataSource> {

Also, make sure you are setting self as the picker view delegate and data source when you create it:

//PICKER AREA
pickerList = [[NSMutableArray alloc] init];
[pickerList addObject:@"aaa"];
[pickerList addObject:@"bbb"];

CGRect pickerFrame = CGRectMake(0, 200, 0, 0);
pickerView = [[UIPickerView alloc] initWithFrame:pickerFrame];
pickerView.showsSelectionIndicator = YES; 
pickerView.dataSource = self;
pickerView.delegate = self;