Question

[Compiler error] prefix attribute must be followed by an interface or protocol stack overflow
Code worked fine in prev. project. I feel like an idiot for posting such a simple question. whats wrong with this stuff?

#import <UIKit/UIKit.h>
#import "FlipsideViewController.h"

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate>
<UIPickerViewDelegate><UIPickerViewDataSource>

@property (strong, nonatomic) IBOutlet UITextField *inputText;
@property(strong, nonatomic) IBOutlet UIPickerView *picker;
@property(strong, nonatomic) IBOutlet UILabel *resultLabel;
@property(strong, nonatomic) NSArray *_convertFrom;
@property(strong, nonatomic) NSArray *_convertTo;
@property(strong, nonatomic) NSArray *_convertRates;
@property(strong, nonatomic) IBOutlet UILabel *formelLabel;
@property(strong, nonatomic) IBOutlet UITextField *inputText;


-(IBAction)textFieldReturn:(id)sender;
-(IBAction)backgroundTouched:(id)sender;


@end

Answer 1

You declare conformation to multiple protocols like this:

@interface MainViewController : UIViewController <FlipsideViewControllerDelegate, UIPickerViewDelegate, UIPickerViewDataSource>

Not with multiple angle bracket sets.