Flutter error Method “contains” can't be unconditionally

Question

I havea bug where my code cant be build because this errorr can someone look my code here the code

Text(
                    "Login", 
                    style: Theme.of(context).textTheme.headline2,
                    ),
                    SizedBox(height: 20,),
                    new TextFormField(
                      keyboardType: TextInputType.emailAddress,
                      validator: (input) => !input.contains("@")
                        ? "Email id Should be Valid"
                        : null,
                    
                    )
              ],
              ),
              ),
            ),

it show error message "The method 'contains' can't be unconditionally invoked because the receiver can be 'null' try making the call conditional (using '?.' or adding a null check to target

can someone please fix my bug thanks before

Answer 1

You need to use:

TextFormField(
   keyboardType: TextInputType.emailAddress,
   validator: (input) => !(input?.contains("@") ?? false)
      ? "Email id Should be Valid"
      : null,
)

As per the official documentationFormFieldValidator , the validator parameter is an optional String. So you need to convert that to non-nullable String first.