[Objective-C] テキスト量に応じてTextViewを可変対応させる ref: http://qiita.com/edo_m18/items/a345a8d1d551e88d4013

file0.m

aTextView.textContainer.lineFragmentPadding = 0;
aTextView.textContainerInset = UIEdgeInsetsZero;

file1.m

UITextView *aTextView = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, 200, 0)];
aTextView.text = @"...some long text...";

// 200, 400のサイズ内に収まるサイズを取得
CGSize size = [aTextView.text sizeWithFont:self.textView.font
                         constrainedToSize:CGSizeMake(200, 400)];

CGRect frame = aTextView.frame;
frame.size.height = size.height;
aTextView.frame = frame;

file2.m

CGSize checkSize = CGSizeMake(200, 400);
NSDictionary *attributes = @{NSForegroundColorAttributeName:[UIColor whiteColor],
NSFontAttributeName:[UIFont systemFontOfSize:12.0]};
NSAttributedString *string = [[NSAttributedString alloc] initWithString:@"some string"
                                                             attributes:attributes];

UITextView *aTextView = [[UITextView alloc] init];
aTextView.attributedText = string;

CGRect textFrame = [string boundingRectWithSize:checkSize
                                        options:NSStringDrawingUsesLineFragmentOrigin
                                        context:nil];
aTextView.frame = textFrame;

file3.m

UITextView *aTextView = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, 200, 0)];
aTextView.text = @"some text.";

// 設定されたテキストのレンダリング結果を得るため、若干の遅延を挟む
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_MSEC)), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    CGRect newFrame = aTextView.frame;
    newFrame.size.height = aTextView.contentSize.height;
    aTextView.frame = newFrame;
});