MINOR: allowing to load submission from other steps easily and set them as default values

README.md

@@ -329,7 +329,49 @@ This new method you create would then become available in the progress indicator
 template.
 
 
-### 7. Finishing it up
+### 7. Loading values from other steps
+
+There are several use cases were you want to pre-populate a value based
+based on the submission value of another step. There are two methods supporting this:
+
+* `getValueFromOtherStep()` load any submitted value from another step from the session
+* `copyValueFromOtherStep()` saves you the repeated work of adding the same lines of code again and again.
+
+Here is an example of how to populate the email address from step 1 in step2 :
+
+	:::php
+	<?php
+
+	class Step1 extends MultiFormStep
+	{
+		public static $next_steps = 'Step2';
+
+		public function getFields() {
+			return new FieldList(
+				new EmailField('Email', 'Your email')
+			);
+		}
+	}
+
+	class Step2 extends MultiFormStep
+	{
+		public static $next_steps = 'Step3';
+
+		public function getFields() {
+			$fields = new FieldList(
+				new EmailField('Email', 'E-mail'),
+				new EmailField('Email2', 'Verify E-Mail')
+			);
+
+			// set the email field to the input from Step 1
+			$this->copyValueFromOtherStep($fields, 'Step1', 'Email');
+
+			return $fields;
+		}
+	}
+
+
+### 8. Finishing it up
 
 Now that we've got a structure set up to collect form data along each step, and
 progress through successfully, we need to customise what happens at the end of 
@@ -394,7 +436,7 @@ Here is an example of what we could do here:
 	}
 
 
-#### 8. Organisation data model
+#### 9. Organisation data model
 
 The class Organisation is mentioned in the above example but doesn't exist at 
 the moment (unlike the existing Member() class which looks after the member 

code/model/MultiFormStep.php

@@ -79,6 +79,13 @@ class MultiFormStep extends DataObject {
 	 */
 	protected $extraClasses = array();
 
+	/**
+	 * Temporary cache to increase the performance for repeated look ups.
+	 *
+	 * @var array $cache
+	 */
+	protected $cache = array();
+
 	/**
 	 * Form fields to be rendered with this step.
 	 * (Form object is created in {@link MultiForm}.
@@ -410,4 +417,43 @@ class MultiFormStep extends DataObject {
 	public function getExtraClasses() {
 		return join(' ', array_keys($this->extraClasses));
 	}
+
+	/**
+	 * Returns the submitted value, if any, of any steps.
+	 *
+	 * @todo  to be removed once https://github.com/silverstripe/silverstripe-multiform/pull/55 is merged in
+	 *
+	 * @param string $fromStep
+	 * @param string $key
+	 * @return mixed
+	 */
+	public function getValueFromOtherStep($fromStep, $key) {
+		// load the steps in the cache, if this one doesn't exist
+		if (!array_key_exists('steps_' . $fromStep, $this->cache)) {
+			$steps = MultiFormStep::get()->filter('SessionID', $this->form->session->ID);
+
+			if($steps) foreach($steps as $step) {
+				$this->cache['steps_' . $step] = $step->loadData();
+			}
+		}
+
+		// check both as PHP isn't recursive
+		return (isset($this->cache['steps_' . $fromStep]) && isset($this->cache['steps_' . $fromStep][$key])) ?
+			$this->cache['steps_' . $fromStep][$key] : null;
+	}
+
+	/**
+	 * allows to get a value from another step copied over
+	 *
+	 * @param FieldList $fields
+	 * @param string    $formStep
+	 * @param string    $fieldName
+	 * @param string    $fieldNameTarget (optional)
+	 */
+	public function copyValueFromOtherStep(FieldList $fields, $formStep, $fieldName, $fieldNameTarget = null) {
+		// if a target field isn't defined use the same fieldname
+		if (!$fieldNameTarget) $fieldNameTarget = $fieldName;
+
+		$fields->fieldByName($fieldNameTarget)->setValue($this->getValueFromOtherStep($formStep, $fieldName));
+	}
 }