ios UIBarButtonItem rightBarButtonItem Title 设置不了

// rightBarButtonItem Title 设置了不起作用，非要在alloc的时候就设置title才有效
UIBarButtonItem *rightBarItem = [[UIBarButtonItem
alloc]initWithTitle:@"退出"
style:UIBarButtonItemStyleBordered
target:self
action:@selector(logout)];
self.navigationItem.rightBarButtonItem = rightBarItem;
//设置颜色，字体大小
[self.navigationItem.rightBarButtonItem
setTitleTextAttributes:[NSDictionary
dictionaryWithObjectsAndKeys:[UIFont
boldSystemFontOfSize:14],
UITextAttributeFont, [UIColor
whiteColor], UITextAttributeTextColor,
nil] forState:UIControlStateNormal];