combined validation logic in Flutter form

Question

I have a form which contains a number of TextFormField similar to this one:

                Container(
              alignment: Alignment.topCenter,
              width: halfMediaWidth-40,
              child: MyTextFormField(
                hintText: 'Food Name',
                validator: (String value) {
                  if (value.isEmpty) {
                    return 'Enter food name';
                  }
                  return null;
                },
                onSaved: (String value) {
                  model.name = value;
                },
              ),
            )

In the above widget, the validation is based on its own value. I have a scenario that the validation is to base on more than one TextFormField's value. For example, if the values of two TextFormFields' value are empty, then return error. How can this be accomplished?

Answer 1

You can pass an instance of TextEditingController to other form fields and then you can use those instances to get the value anytime. An example is here

var controller1 = TextEditingController();
var controller2 = TextEditingController(); 

//form field 1
MyTextFormField(
controller:controller1,   // passed controller 1
                hintText: 'Food Name',
                validator: (String value) {
                  if (value.isEmpty) {
                    return 'Enter food name';
                  }
                  return null;
                },
                onSaved: (String value) {
                  model.name = value;
                },
              ),
            ),
//form field 2
MyTextFormField(
controller:controller2, // passed controller 2
                hintText: 'Food Name',
                validator: (String value) {
        // you can use value like below to check value for formfield 1 like below
                  if (controller1.value.isEmpty && value.isEmpty) { 
                    return 'Enter food name';
                  }
                  return null;
                },
                onSaved: (String value) {
                  model.name = value;
                },
              ),
            )