Posts Tagged ‘yaml’

Sometimes you need to put a constraint on a whole class, rather than a single value. Duplicate usernames are a good example of this – you don’t want to be able to set a username to one that is already in use – but if it is in use with the user you are currently working on, you don’t want to flag it up as an error!

Lets use that as an example. You have a Username constraint and a UsernameValidator object to do the actual validation. We need to supply the validator an object, so we need to put the following method inside the Username object.

public function getTargets()
{
    return self::CLASS_CONSTRAINT;
}

This will turn the first parameter in our isValid function in the UsernameValidator class to an object.

public function isValid($user, Constraint $constraint)

Finally, you can call the constraint from your YAML validation file.

User:
    constraints:
        - nocs:UniqueUsername: ~

Normally, under user you would have getters and properties – but here we’re adding a new section named “constraints” which lists all the class constraints.

If you are trying to install YAML via PECL on Lion, you may get an error such as the following.

configure: error: Please install libyaml
ERROR: `/private/tmp/pear/install/yaml/configure --with-yaml' failed

Some solutions on the internet suggest installing it via a package manager.

rvm pkg install libyaml

However, although this process will claim to work, when you come to run the command again, it will fail at the same point. Instead, you need to download libyaml, which you can do here, then extract it, cd into the directory and run the following commands.

./configure
make
make install

You don’t need to sudo. You should now be able to run the install command again.

sudo pecl install --ignore-errors yaml

This time it should be successful.

If you are trying to install PECL YAML on Mac OS X Lion, you may find you get a conflict with an error message similar to the following.

WARNING: pecl.php.net/yaml: conflicting files found:
yaml/LICENSE (pear.symfony-project.com/yaml)

This error is documented on GitHub and as it is not critical, can be overcome by turning off errors.

pecl install --ignore-errors yaml

On running that command, it should no longer stop at that point.

If you’re using YAML in Ruby and have it installed via RVM, you might get a notice similar to the following.

It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.

You can solve this using the following commands.

rvm pkg install libyaml
rvm reinstall 1.9.3

You may (or even need) to replace 1.9.3 with your exact version number.

The Symfony2 framework comes with a really nice validation library and on top of the built in constraints that you can use you also have the ability to add your own custom constraints to perform any other validation checks you need to do.

The Cookbook has an article on how to create such a custom constraint, but unfortunately, as has happened a few times with the Symfony2 documentation, it misses out some fundamental and sometimes rather obscure step in order to get it working.

The problem is, it doesn’t tell you where to put the files. That leaves two options – either you have somewhere they need to be in order for Symfony to find them, or you need to fell Symfony where they are.

After hours of digging around, we eventually found the answer – in your validation.yml file you need to register the namespace and then reference that name when you call the validation rules.

Start by registering the namespace at the top of your validation.yml file.

namespaces:
  myValidator: Acme\ExampleBundle\Validator\

Lets say you have added a custom validation constraint called Postcode. When you want to invoke that from your validation rules, you need to reference the namespace you have just created.

postcode:
    - myValidator:Postcode: ~

You can then use this namespace with your custom validation rules, place them in the appropriate directory (in this case src/ExampleBundle/Validator, but you can store them somewhere else if you change the namespace – remember that Symfony2 will extract the path from the namespace).