UILabel自适应高度和自动换行

-(CGSize)sizeWithString:(NSString *)string

{

    UIFont *font = [UIFontfontWithName:@"Arial"size:15];

    CGSize size =CGSizeMake(180,200);

    CGSize labelsize = [stringsizeWithFont:font constrainedToSize:sizelineBreakMode:NSLineBreakByWordWrapping];

    return labelsize;

}