原生的UIAlertController字體靠中，看到高人hack出如何改變字體特性，終於豁然開朗呢！
知道之後，自己學著如何hack吧！
/**
Theme: UIAlertController Text Alignment
IDE: Xcode 8
Language: Objective C
Date: 105/12/14
Author: HappyMan
Blog: https://cg2010studio.wordpress.com/
*/
UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"確定要兌換嗎？"
message:message
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * _Nonnull action) {
}];
[alert addAction:cancelAction];
UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"確定"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * _Nonnull action) {
}];
[alert addAction:okAction];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
paragraphStyle.alignment = NSTextAlignmentLeft;
NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc] initWithString:message attributes:@{NSParagraphStyleAttributeName:paragraphStyle}];
[alert setValue:attributedStr forKey:@"attributedMessage"];
[self presentViewController:alert animated:YES completion:nil];
這裡的重點是這個key：attributedMessage。
逍遙文工作室 
隨意留個言吧：）～