title: Text in Button doesn't show text in ios (native base)
body: <p>hi in my project I use <code>nativeBase</code>. I use <code>&lt;Button&gt;&lt;Text&gt;blablabla&lt;/Text&gt;&lt;/Button&gt;</code>
  when running in android ok but when run-ios text not showing.
  this is my component :</p>
  
  <pre class="lang-js prettyprint-override"><code>&lt;View style={{ marginLeft: 7, flexDirection: 'column', alignItems: 'center', justifyContent: 'center' }}&gt;
    &lt;View style={styles.btncontent}&gt;
      &lt;Right style={{ flex: 0.2 }}&gt;
        &lt;Image source={mapBtnLogo} style={styles.btnImage} /&gt;
      &lt;/Right&gt;
      &lt;Left style={{ flex: 0.8 }}&gt;
        &lt;Button full transparent style={styles.btn} onPress={() =&gt; props.myProps.gotoMap([section.YPOINT, section.XPOINT])}&gt;
          &lt;Text style={styles.btnText}&gt;
            نمایش روی نقشه
                  &lt;/Text&gt;
        &lt;/Button&gt;
      &lt;/Left&gt;
    &lt;/View&gt;
  &lt;/View&gt;
  </code></pre>
  
  <p>and this is <code>styles</code> :</p>
  
  <pre class="lang-js prettyprint-override"><code>const styles = StyleSheet.create({
    ...Platform.select({
      ios: {
        btnImage: {
          margin: 5,
          marginRight: 20,
          width: moderateScale(20),
          height: moderateScale(20),
        },
        btn: {
          //alignItems: 'flex-start',
          width: '100%',
          height: '10%',
  
        },
        btnText: {
          fontFamily: 'IRANSansMobile',
          fontSize: 15,
          color: '#000',
        },
      }, android: {
        btn: {
          width: '100%',
          height: '10%',
        },
        btnText: {
          fontFamily: 'IRANSansMobile',
          fontSize: 15,
          color: '#000000'
        },
        btncontent: {
          backgroundColor: '#59c5b8',
          flexDirection: 'row-reverse',
          alignItems: 'center',
          borderWidth: 0.3,
          borderRadius: 5,
          marginLeft: 10,
          width: '95%',
        },
      }
  </code></pre>
  
  <p>remove <code>node module</code> and install again not working.
  and clear Xcode and run again but not working.
  I read this post <a href="https://stackoverflow.com/questions/51888060/nativebase-button-doesnt-show-text">NativeBase Button doesn't show text</a> but I don't use <code>padding</code> and still not showing text</p>