So you are inside your for loop with an i index. What we are looking here is to assign a UIPickerView as each textfield's input view. Try something like this...
//FOR LOOP BEGINS
//Iteration - Create a textfield.
[self.view addSubview:yourTextfield];
//Assign a uipickerview as textfield's input view.
UIPickerView *pickerView = [[UIPickerView alloc] init];
pickerView.frame = CGRectMake(0,0,300,300);
pickerView.tag = i;
pickerView.delegate = self;
pickerView.showsSelectionIndicator = YES;
textField.inputView = pickerView;
[self.view addSubview:pickerView];
//Iteration ends
//FOR LOOP ENDS
P.S. You can also add a toolbar with each pickerView to your textfield using the inputAccessoryView