Form validation rules in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a TextFormField with a validator that checks if the input is empty.

Flutter

TextFormField(
  validator: (value) {
    if (value == null || value[1] '') {
      return 'Please enter some text';
    }
    return null;
  },
)

Drag options to blanks, or click blank then click option'

A==

B!=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' causes the validator to fail incorrectly.

Using comparison operators like '>' or '<' on strings causes errors.

The validator checks if the input value is null or equals an empty string using ==.

2fill in blank

medium

Complete the code to add a validator that checks if the input length is at least 6 characters.

Flutter

TextFormField(
  validator: (value) {
    if (value == null || value.length [1] 6) {
      return 'Enter at least 6 characters';
    }
    return null;
  },
)

Drag options to blanks, or click blank then click option'

A>

B>=

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' instead of '<' causes the validator to accept short inputs.

Using '==' only checks for exact length 6, not less.

The validator returns an error if the input length is less than 6 characters, so the operator is <.

3fill in blank

hard

Fix the error in the validator to correctly check if the input contains '@' for an email field.

Flutter

TextFormField(
  validator: (value) {
    if (value == null || !value[1]('@')) {
      return 'Enter a valid email';
    }
    return null;
  },
)

Drag options to blanks, or click blank then click option'

Acontains

BindexOf

Chas

Dincludes

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'indexOf' without comparing to -1 causes errors.

Using 'has' or 'includes' are not valid Dart String methods.

The Dart String method contains checks if the string includes a substring.

4fill in blank

hard

Fill both blanks to create a validator that checks if the input is not empty and contains a dot '.' character.

Flutter

TextFormField(
  validator: (value) {
    if (value == null || value[1] '' || !value[2]('.')) {
      return 'Enter a valid input';
    }
    return null;
  },
)

Drag options to blanks, or click blank then click option'

A==

B!=

Ccontains

DstartsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' for the empty string check causes wrong validation.

Using 'startsWith' instead of 'contains' misses dots inside the string.

The first blank checks if the input equals an empty string, the second checks if it contains a dot.

5fill in blank

hard

Fill all three blanks to create a validator that checks if the input is not empty, has length greater than 5, and contains '@'.

Flutter

TextFormField(
  validator: (value) {
    if (value == null || value[1] '' || value.length [2] 5 || !value[3]('@')) {
      return 'Enter a valid email';
    }
    return null;
  },
)

Drag options to blanks, or click blank then click option'

A==

B>

Ccontains

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for length check.

Using '!=' for empty string check causes wrong validation.

The validator checks if the input is empty (== ''), length is greater than 5 (> 5), and contains '@'.