iOS UITextFeild获取高亮部分的长度

获取原因：

　　中英文混输时，会遇到长度统计不准的问题。

获取方法：

 NSString *toBeString = textField.text;
   NSString *lang = [[UITextInputMode currentInputMode] primaryLanguage]; // 键盘输入模式
   if ([lang isEqualToString:@"zh-Hans"]) { // 简体中文输入，包括简体拼音，健体五笔，简体手写
       UITextRange *selectedRange = [textField markedTextRange];
       //获取高亮部分
       UITextPosition *position = [textField positionFromPosition:selectedRange.start offset:0];
       // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
       if (!position) {
           if (toBeString.length > kMaxLength) {
               textField.text = [toBeString substringToIndex:kMaxLength];
           }
       }
       // 有高亮选择的字符串，则暂不对文字进行统计和限制
       else{
       }
   }
   // 中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
   else{
       if (toBeString.length > kMaxLength) {
           textField.text = [toBeString substringToIndex:kMaxLength];
       }
   }

h1, h2, h3, h4, h5, h6, p, blockquote { margin: 0; padding: 0 }
body { font-family: "Helvetica Neue", Helvetica, "Hiragino Sans GB", Arial, sans-serif; font-size: 13px; line-height: 18px; color: rgba(115, 115, 115, 1); background-color: rgba(255, 255, 255, 1); margin: 10px 13px }
table { margin: 10px 0 15px; border-collapse: collapse }
td, th { border: 1px solid rgba(221, 221, 221, 1); padding: 3px 10px }
th { padding: 5px 10px }
a { color: rgba(0, 105, 214, 1) }
a:hover { color: rgba(0, 80, 163, 1); text-decoration: none }
a img { border: none }
p { margin-bottom: 9px }
h1, h2, h3, h4, h5, h6 { color: rgba(64, 64, 64, 1); line-height: 36px }
h1 { margin-bottom: 18px; font-size: 30px }
h2 { font-size: 24px }
h3 { font-size: 18px }
h4 { font-size: 16px }
h5 { font-size: 14px }
h6 { font-size: 13px }
hr { margin: 0 0 19px; border-top: 0; border-right: 0; border-bottom: 1px solid rgba(204, 204, 204, 1); border-left: 0 }
blockquote { padding: 13px 13px 21px 15px; margin-bottom: 18px; font-family: georgia, serif; font-style: italic }
blockquote:before { content: "“"; font-size: 40px; margin-left: -10px; font-family: georgia, serif; color: rgba(238, 238, 238, 1) }
blockquote p { font-size: 14px; font-weight: 300; line-height: 18px; margin-bottom: 0; font-style: italic }
code, pre { font-family: Monaco, Andale Mono, Courier New, monospace }
code { background-color: rgba(254, 233, 204, 1); color: rgba(0, 0, 0, 0.75); padding: 1px 3px; font-size: 12px; -webkit-border-radius: 3px; -moz-border-radius: 3px; border-radius: 3px }
pre { display: block; padding: 14px; margin: 0 0 18px; line-height: 16px; font-size: 11px; border: 1px solid rgba(217, 217, 217, 1); white-space: pre-wrap; word-wrap: break-word }
pre code { background-color: rgba(255, 255, 255, 1); color: rgba(115, 115, 115, 1); font-size: 11px; padding: 0 }
sup { font-size: 0.83em; vertical-align: super; line-height: 0 }
* { -webkit-print-color-adjust: exact }
@media screen and (min-width: 914px) { body { width: 854px; margin: 10px auto } }
@media print { body, code, pre code, h1, h2, h3, h4, h5, h6 { color: rgba(0, 0, 0, 1) } table, pre { page-break-inside: avoid } }