月と日だけを選択するピッカ．iPhone用．

UIMonthAndDayPickerView.m

#define _COMPONENT_MONTH_LABEL 0
#define _COMPONENT_DAY_LABEL 1

@implementation UIMonthAndDayPickerView
@synthesize month, day;
- (id)initWithFrame:(CGRect)aRect {
    if ([super initWithFrame:aRect] != nil) {
        self.delegate = self;
        self.dataSource = self;
        self.showsSelectionIndicator = YES;
    }
    month = day = 1;
    return self;
}
- (void)dealloc {
    [super dealloc];
}
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 2;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    if(component == _COMPONENT_MONTH_LABEL) {
        return 12;
    } else if (component == _COMPONENT_DAY_LABEL) {
        switch([self selectedRowInComponent:_COMPONENT_MONTH_LABEL]){
            case 1:
                return 29;
            case 3:
            case 5:
            case 8:
            case 10:
                return 30;
            default:
                return 31;
        }
    } else {
        return 0;
    }
}

- (NSString*)pickerView: (UIPickerView*) pView titleForRow:(NSInteger)row 
           forComponent:(NSInteger)component { 
    switch (component) {
        case _COMPONENT_MONTH_LABEL:
            return [NSString stringWithFormat:@"%d 月 ", row+1];
        case _COMPONENT_DAY_LABEL:
            return [NSString stringWithFormat:@"%d 日", row+1];
        default:
            return @"";
    }
} 

- (void)pickerView:(UIPickerView *)pickerView 
      didSelectRow:(NSInteger)row 
       inComponent:(NSInteger)component {
    [self reloadComponent:_COMPONENT_DAY_LABEL];
    month = [self selectedRowInComponent:_COMPONENT_MONTH_LABEL] + 1;
    day = [self selectedRowInComponent:_COMPONENT_DAY_LABEL] + 1;
}

@end