IOS7笔记-６、控制器多态性、导航控制器、选项卡栏控制器

１、遍历符合条件字符

-(NSAttributedString *)charactersWithAttribute:(NSString *)attributeName
{
    NSMutableAttributedString *characters = [[NSMutableAttributedString alloc] init];
    
    int index = 0;
    while (index < [self.textToAnalyze length]) {
        NSRange range;
        id value = [self.textToAnalyze attribute:attributeName
                                         atIndex:index
                                  effectiveRange:&range];
        if (value) {
            [characters appendAttributedString:[self.textToAnalyze attributedSubstringFromRange:range]];
            index = range.location + range.length;
        } else {
            index++;
        }
    }
    
    return characters;
}

-(void)updateUI
{
    self.colorfulCharactersLabel.text = [NSString stringWithFormat:@"%d colorful characters", [[self charactersWithAttribute:NSForegroundColorAttributeName] length]];
    self.outlinedCharactersLabel.text = [NSString stringWithFormat:@"%d outlined characters", [[self charactersWithAttribute:NSStrokeWidthAttributeName] length]];
}

２、segue识别代码

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"Analyze Text"]) {
        if ([segue.destinationViewController isKindOfClass:[TextStatsViewController class]]) {
            TextStatsViewController *tsvc = (TextStatsViewController *)segue.destinationViewController;
            tsvc.textToAnalyze = self.body.textStorage;
        }
    }
}