cakephp 3.0 $this->output function does not exist error - cakephp

Question

I am using the image helper of 2.x in my cakephp 3.x application but i am facing a problem with this that in my cakephp 2.x the function return the value as below code
return $this->output(sprintf($this->Html->_tags['image'], $this->webroot($relfile), $this->Html->_parseAttributes($htmlAttributes, null, '', ' ')), $return);
but in cakephp 3.x output and _parseAttributes function is removed so i dont know how to use these two function in cakephp 3.x
_parseAttributes function contain the image related data like 'class', 'alt' other things
i have searched a lot on net for output function in cake 3.x but did not find any successfull solution please try to help me
Thanks

Answer 1

Use the Html helper
There's nothing in your example code that justifies the use of custom code for generating the tag, so you could simply use the Html helper instead
// ...
class YourCustomHelper extends Helper
{
public $helpers = [
'Html',
// ...
];
public function someMethod($relfile, array $htmlAttributes)
{
$options = $htmlAttributes + ['pathPrefix' => false];
return $this->Html->image($url, $options);
}
// ...
}
Note the use of the pathPrefix option, since it looks like you want to point to a custom path, you should disable it, as otherwise you may end up with the default image base URL being prepended to the path.
Custom tags and attributes
If you'd really need a custom solution that isn't already covered by other helpers, then the replacement for output() and _parseAttributes() are return and string templates.
For the sake of supplying an example, here's a trimmed down one of what HtmlHelper::image() does:
use Cake\Core\Configure;
use Cake\View\StringTemplateTrait;
// ...
class YourCustomHelper extends Helper
{
use StringTemplateTrait;
protected $_defaultConfig = [
'templates' => [
'someTemplate' => '<img src="{{url}}"{{attrs}}/>',
],
// ...
];
public $helpers = [
'Url',
// ...
];
public function someMethod($relfile, array $htmlAttributes = [])
{
$url = $this->Url->assetUrl($relfile);
$templater = $this->templater();
return $templater->format('someTemplate', [
'url' => $url,
'attrs' => $templater->formatAttributes($htmlAttributes),
]);
}
// ...
}
This should be pretty much self explantory, you include the StringTemplateTrait that holds the templating functionality, define a custom template, and format it using the templater.
Note the use of the Url helper, it will do all the necessary stuff like encoding the URL, timestamping it, adding the webroot path, etc...
See also
Cookbook > Views > Helpers > Configuration options
Source > \Cake\View\Helper\HtmlHelper::image()
API > \Cake\View\Helper\UrlHelper::assetUrl()
API > \Cake\View\StringTemplate::format()
API > \Cake\View\StringTemplate::formatAttributes()
Cookbook > Appendices > 3.0 Migration Guide > Helpers