title: pass emoji unicode from cpp core-level to ios ui level
body: <p>In c++ level I want to change emoji string like <code>":smile:"</code> to unicode <code>"\u{1f604}"</code> which ios supported.
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  However, C++ doesn't support that type, <code>\u</code> must follow with digit. Then I change unicode to <code>"\\u{1f604}"</code>. Now, it can work well in c++ level, but when I pass this string to ios level, ios won't change this string to emoji automatically.
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  Could you please give me some ideas?<br>
  <br/>
  I am sorry that I didn't describe it clearly.
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  In my project, I parse json from server in C++ level and then I pass this data to IOS level.</p>