validation_extensions

Description:

validation extensions

validation_extensions #
Flutter form field validations using dart extension methods.
Available validation extension methods #
String extension methods #
Check tests file for examples on how to use them or the example app.



Method
Parameters
Description




isRequired
None
Validates if the string in not empty


isEmail
None
Validates if the string is a valid email address


minLength
int min
Validates if the string length is longer than min


maxLength
int max
Validates if the string length is shorter than max


lengthRange
int min, int max
Validates if the string length is longer than min and shorter than max


match
String stringToMatch
Validates if the string is an exact match of the String stringToMatch parameter that you provide


matchPattern
String regExp
Validates if the string matches the regular expression regExp parameter that you provide


isInt
None
Validates if the string is a valid integer


isDouble
None
Validates if the string is a valid double


min
int min
Validates if the string is a valid double bigger than min


max
int max
Validates if the string is a valid double smaller than max


range
int min, int max
Validates if the string is a valid double between min and max



Note
You have to use isRequired to make a field mandatory, all other extension methods won't validate empty string, and will validate only if string is not empty which will make the field optional.
List<Function> extension methods #



Method
Description




validate
execute validation functions one by one, will stop execution when it encounter a validation error and return the errorText



Usage #
All extension methods return type is Function, you have to use double parentheses to execute the returned function for single validations.
Form(
key: _formKey,
child: TextFormField(
validator: (v) => v.isRequired()(),
),
),
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Multi validations #
For multi rules validation put your validation in a list and call validate() extension method on the list, it will execute validation one by one, it will stop execution when it encounter the first validation error and return the errorText to increase performance.
Form(
key: _formKey,
child: Column(
children: <Widget>[
TextFormField(
onChanged: (v) => password = v,
validator: (v) => [
v.isRequired(),
v.minLength(8),
].validate(),
),
TextFormField(
validator: (v) => [
v.isRequired(),
v.match(password),
].validate(),
),
],
),
),
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Custom validations #
If you want to use you own validations in multi rule validation, your validation rules must be:
Function that returns a Function that returns a String.
Function customValidation(v) {
return(){
return v != "Validation logic" ? "Invalid input" : null;
};
}

Form(
key: _formKey,
child: TextFormField(
autovalidate: true,
validator: (v) => [
v.isRequired(),
customValidation(v),
].validate(),
),
),
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Custom error message #
Pass the optional named parameter errorText to the extension method to override the default error message
Form(
key: _formKey,
child: TextFormField(
onChanged: (v) => password = v,
validator: (v) => [
v.isRequired(
errorText: "Password is required",
),
v.minLength(
8,
errorText: "Password can not be less than 8 characters",
),
].validate(),
),
),

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