How to add min value for a field in custom Module system.xml file?

Question

I want to add minimum value attribute for a admin interface field in my custom module. Can anyone suggest me how I can add min attribute in field? Here is my system.xml code:

<field id="uspsintexpress" translate="label" type="text" sortOrder="70" showInDefault="1" showInWebsite="1" showInStore="1">
<label>USPS Int'l Express Days</label>
</field>

Answer 1

Option 1

You can add minimum value validation by backend_model, for example.

<field id="base_url" translate="label comment" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">
    <label>Base URL</label>
    <backend_model>Magento\Config\Model\Config\Backend\Baseurl</backend_model>
    <comment>Specify URL or {{base_url}} placeholder.</comment>
</field>

Then you can find the beforeSave method at \m9agento210\vendor\magento\module-config\Model\Config\Backend\Baseurl.php

public function beforeSave()
{
    $value = $this->getValue();
    try {

       // You can write some validation here.

    } catch (\Magento\Framework\Exception\LocalizedException $e) {

        throw $error;
    }
}

This is an example, you can implement this in your custom module.

Option 2

        <field id="custom_email" translate="label comment" sortOrder="0" type="text" showInDefault="1" showInWebsite="0" showInStore="0">
            <label>Enter Email Id</label>
            <validate>validate-email</validate>
        </field>

Some Important validation classes are

'validate-no-html-tags'         => 'HTML tags are not allowed'
'validate-select'               => 'Please select an option.'
'required-entry'                => 'This is a required field.'
'validate-number'               => 'Please enter a valid number in this field.'
'validate-digits'               => 'Please use numbers only in this field. Please avoid spaces or other characters such as dots or commas.'
'validate-date'                 => 'Please enter a valid date.'
'validate-email'                => 'Please enter a valid email address. For example johndoe@domain.com.'
'validate-url'                  => 'Please enter a valid URL. Protocol is required (http://, https:// or ftp://)'
'validate-not-negative-number'  => 'Please enter a number 0 or greater in this field.'
'validate-zero-or-greater'      => 'Please enter a number 0 or greater in this field.'
'validate-state'                => 'Please select State/Province.'
'validate-cc-number'            => 'Please enter a valid credit card number.'
'validate-data'                 => 'Please use only letters (a-z or A-Z), numbers (0-9) or underscore(_) in this field, first character should be a letter.'

Hope it helps.

Answer 2

Finally, I got Solution for my Question. Here is solution system.xml code:

<field id="uspsintexpress" translate="label" type="text" sortOrder="70" showInDefault="1" showInWebsite="1" showInStore="1">
<label>USPS Int'l Express Days</label>
<validate>validate-greater-than-zero</validate>
</field>