Skip to main content

This site requires you to update your browser. Your browsing experience maybe affected by not having the most up to date version.

We're retiring the forums!

The SilverStripe forums have passed their heyday. They'll stick around, but will be read only. We'd encourage you to get involved in the community via the following channels instead:

Template Questions /

Moderators: martimiz, Sean, Ed, biapar, Willr, Ingo, swaiba

Extending StringField Class - "Trying to get property of non-object" Error Message


Go to End


3 Posts   2024 Views

Avatar
_Matt

Community Member, 29 Posts

10 May 2013 at 10:50am

Edited: 10/05/2013 10:51am

I've written an extension called 'StringToKey' that converts a template value, such as $Title, into lowercase with the spaces changed into hyphens - a bit like when you do $Title.LowerCase, or $Title.UpperCase.

In my case I'm converting menu titles in my template, like this (in a Menu loop):

<ul class="submenu $Title.StringToKey">

It is working (the values are correctly output in the template), but I'm also getting a big error message at the top of the page:

"[Notice] Trying to get property of non-object"

It then highlights this line in my code:

$title = $this->owner->value;

Can anyone suggest why this might be happening, I'm a bit stuck? Here's my full code:

<?php
class StringToKey extends Extension
{
    /**
     * Return StringToKey
     *
     * @return string
     */
    public function StringToKey()
    {
        $title = $this->owner->value;

        if ($title != null)
        {
            return $this->convertString($title);
            // var_dump($this->convertString($title));
        }
        else
        {
            return false;
        }
    }

    /**
     * Convert string to lowercase and replace spaces with hyphens
     *
     * @return string
     */
    protected function convertString($string)
    {
        // Lower case everything
        $string = strtolower($string);
        // Make alphaunermic
        $string = preg_replace("/[^a-z0-9_\s-]/", "", $string);
        // Clean multiple dashes or whitespace
        $string = preg_replace("/[\s-]+/", " ", $string);
        // Convert whitespace and underscores to hyphens
        $string = preg_replace("/[\s_]/", "-", $string);
        return $string;
    }
}

Avatar
_Matt

Community Member, 29 Posts

12 May 2013 at 1:23am

I worked out that the reason for the error was because the first result being returned was 'null'. Not sure why though?

Anyway, I added an additional check to filter out this error:

public function StringToKey()
{
    if (!$this->owner instanceof Varchar) {
        return false;
    }

    $title = $this->owner->value;
    if ($title != null) {
        return $this->convertString($title);
        // var_dump($this->convertString($title));
    } else {
        return false;
    }
}

Not sure if this is the best way to do things, but it's the only thing I could think of.

Avatar
jacobjensen

Community Member, 3 Posts

21 May 2016 at 3:07am

Edited: 21/05/2016 3:08am

Hi Matt,
I've tried to implement your code in my own project running 3.3.1 - But I can't seem to make it work...
I've added this to my config.yml

Extension:
  extensions:
    - StringToKey

Any ideas would be appreciated! :-)