Magento – Magento 2 Locked Config Values

Without having access to your source code we wont be able to definitively say where your problem likes.

The first place I would look is at the structure of your model. Can you instantiate it?

$model = Mage::getModel('baka_mama/system_config_source_selectsand_values'); echo get_class($model);

If that returns null or something other than your class then the problem likely likes in not using a correct model name, or the model file / class name combination is incorrect.

If it is being created and matches what you are expecting then post more information about the error. Especially the function where the problem is occurring as you have not identified a line number to be able to see what is happening when it gets that error.

If your helper extends Magento\Framework\App\Helper\AbstractHelper then you don't need to add the ScopeConfigInterface dependency again in your constructor because the parent class already has that dependency.

You can simply do:

$this->scopeConfig->getValue('section/group/field');

Please note that the parent class variable does not start with an underscore.

Same remark for the Context dependency, you do not need to re add it as it's already part of the parent constructor.

FYI, the AbstractHelper constructor looks like this:

public function __construct(Context $context)
{
    $this->_moduleManager = $context->getModuleManager();
    $this->_logger = $context->getLogger();
    $this->_request = $context->getRequest();
    $this->_urlBuilder = $context->getUrlBuilder();
    $this->_httpHeader = $context->getHttpHeader();
    $this->_eventManager = $context->getEventManager();
    $this->_remoteAddress = $context->getRemoteAddress();
    $this->_cacheConfig = $context->getCacheConfig();
    $this->urlEncoder = $context->getUrlEncoder();
    $this->urlDecoder = $context->getUrlDecoder();
    $this->scopeConfig = $context->getScopeConfig();
}