Flutter set validator required or not required

How set TextFormField required or not required?

Eg. If required parameter = true validator: (value) => value!.isEmpty ? ‘Required!’ : null,

if required parameter = false Not required

Widget _textInput({controller, name, enable, autofocus, required}) {
    return Container(
      child: TextFormField(
        autofocus: autofocus,
        enabled: enable,
        cursorColor: Colors.black,
        controller: controller,
        decoration: InputDecoration(
          filled: true,
          fillColor: Colors.white,
          focusedBorder: UnderlineInputBorder(
            borderSide: BorderSide(color: Colors.black45),
          ),

        //if  required true or false change 
        validator: (value) => value!.isEmpty ? 'Required!' : null,

      ),
    );
  }

>Solution :

First of all you need to define you variable with type in constructor for example required should be like this bool required, then you can do this:

Widget _textInput({controller, name, enable, autofocus,bool required}) {
    return Container(
      child: TextFormField(
        autofocus: autofocus,
        enabled: enable,
        cursorColor: Colors.black,
        controller: controller,
        decoration: InputDecoration(
          filled: true,
          fillColor: Colors.white,
          focusedBorder: UnderlineInputBorder(
            borderSide: BorderSide(color: Colors.black45),
          ),
        ),
        validator: required?  (value) => value!.isEmpty ? 'Required!' : null : null,
      ),
    );
  }