一、设置输入内容的长度

1、监听方法

iOS UITextField限制字符长度

2、UITextField代理方法

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString: ALPHANUM ] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    
    if (textField == self.passWordField ) {
        //这里的if时候为了获取删除操作,如果没有次if会造成当达到字数限制后删除键也不能使用的后果.
        if (range.length == 1 && string.length == 0) {
            return YES;
        }
        //so easy
        else if (6<=self.passWordField.text.length && self.passWordField.text.length >=8 ) {
            
            self.passWordField.text = [textField.text substringToIndex:8];
            
            [textField resignFirstResponder];
            
            return NO;
        }
    }else if ( textField == self.repwdField){
        //这里的if时候为了获取删除操作,如果没有次if会造成当达到字数限制后删除键也不能使用的后果.
        if (range.length == 1 && string.length == 0) {
            return YES;
        }
        //so easy
        else if ( 6<=self.repwdField.text.length && self.repwdField.text.length >=8) {
            self.repwdField.text = [textField.text substringToIndex:8];
            [textField resignFirstResponder];
            return NO;
        }
    }
    return [string isEqualToString:filtered];;
}

二、设置占位符文字字体大小、颜色、对齐方式

textField.placeholder = @"xxxx";  
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  
[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];  

//------设置placeholder的大小后，如果不是系统默认大小，会出现垂直不居中的情况，解决如下
NSMutableParagraphStyle *style = [textField.defaultTextAttributes[NSParagraphStyleAttributeName] mutableCopy]; 
style.minimumLineHeight = textField.font.lineHeight - (textField.font.lineHeight - [UIFont systemFontOfSize:13.0f].lineHeight) / 2.0; //[UIFont systemFontOfSize:13.0f]是设置的placeholder的字体 
textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"请输入密码" attributes:@{NSParagraphStyleAttributeName : style}];

//------如果输入文字不居中，placeholder不居中，重写系统方法
-(CGRect)editingRectForBounds:(CGRect)bounds;
-(CGRect)placeholderRectForBounds:(CGRect)bounds;

//设置UITextField的textAlignment属性为NSTextAlignmentRight，placeholder文字也就靠右对齐了,输入光标也从右边开始

三、设置text文字字体大小、颜色

_nameTextField.textColor = [UIColor grayColor];

四、UITextField输入时候，默认文字偏移问题的解决办法

//不要设置清楚样式
//textField.clearButtonMode = UITextFieldViewModeWhileEditing;
textField.textAlignment =NSTextAlignmentRight;