名称不能超过20个字

public/react/src/modules/courses/boards/AddDirModal.js

@@ -22,6 +22,15 @@ class AddDirModal extends Component{
     let coursesId = this.props.match.params.coursesId;
     const url = `/courses/${coursesId}/boards.json`
     let { inputValue } = this.state;
+    if (!inputValue) {
+      this.setState({ errorMsg: '名称不能为空'})
+      return;
+    } 
+    if (inputValue.length > 20) {
+      this.setState({ errorMsg: '名称不能超过20个字'})
+      return;
+    }
+    this.setState({ errorMsg: ''})
 
     axios.post(url,{
         name: inputValue
@@ -36,10 +45,10 @@ class AddDirModal extends Component{
     })
   }
   onCancel = () => {
-    this.setState({ visible: false, inputValue: '' })
+    this.setState({ visible: false, inputValue: '', errorMsg: '' })
   }
   render(){
-    let { inputValue, visible } = this.state;
+    let { inputValue, visible, errorMsg } = this.state;
     const { title } = this.props;
     return(
         <Modal
@@ -61,6 +70,8 @@ class AddDirModal extends Component{
                     onInput={this.onInput}
                 />
              </div>
+
+             {errorMsg && <span style={{color: 'red'}}>{errorMsg}</span>}
              
              {/* {this.state.NavmodalValuetype===true?<span className={"color-red"}>
                  {this.state.NavmodalValues}