前端项目实战贰佰伍拾捌react-admin+material ui-react-admin-admin中AutocompleteInput之shouldRenderSuggestions

<AutocompleteInput 
    source="category"
    choices={choices}
    shouldRenderSuggestions={(val) => 
{ return val.trim().length > 2 }}
/>

什么时候呈现建议的条件