Parameter by name (#5055)

* Add method get_parameter

- Return a parameter for a part, on name

* Add unit test for new method

* Adds template tag to retrieve parameter based on name

* Update docs

InvenTree/part/models.py

@@ -2176,6 +2176,16 @@ class Part(InvenTreeBarcodeMixin, InvenTreeNotesMixin, MetadataMixin, MPTTModel)
 
         return quantity
 
+    def get_parameter(self, name):
+        """Return the parameter with the given name.
+
+        If no matching parameter is found, return None.
+        """
+        try:
+            return self.parameters.get(template__name=name)
+        except PartParameter.DoesNotExist:
+            return None
+
     def get_parameters(self):
         """Return all parameters for this part, ordered by name."""
         return self.parameters.order_by('template__name')
@@ -3598,6 +3608,21 @@ class PartParameter(MetadataMixin, models.Model):
         blank=True,
     )
 
+    @property
+    def units(self):
+        """Return the units associated with the template"""
+        return self.template.units
+
+    @property
+    def name(self):
+        """Return the name of the template"""
+        return self.template.name
+
+    @property
+    def description(self):
+        """Return the description of the template"""
+        return self.template.description
+
     @classmethod
     def create(cls, part, template, data, save=False):
         """Custom save method for the PartParameter class"""

InvenTree/part/test_param.py

@@ -63,6 +63,20 @@ class TestParams(TestCase):
 
             self.assertEqual(len(p.metadata.keys()), 4)
 
+    def test_get_parameter(self):
+        """Test the Part.get_parameter method"""
+
+        prt = Part.objects.get(pk=3)
+
+        # Check that we can get a parameter by name
+        for name in ['Length', 'Width', 'Thickness']:
+            param = prt.get_parameter(name)
+            self.assertEqual(param.template.name, name)
+
+        # Check that an incorrect name returns None
+        param = prt.get_parameter('Not a parameter')
+        self.assertIsNone(param)
+
 
 class TestCategoryTemplates(TransactionTestCase):
     """Test class for PartCategoryParameterTemplate model"""

InvenTree/report/templatetags/report.py

@@ -181,7 +181,7 @@ def encode_svg_image(filename):
 
 
 @register.simple_tag()
-def part_image(part):
+def part_image(part: Part):
     """Return a fully-qualified path for a part image.
 
     Arguments:
@@ -200,6 +200,23 @@ def part_image(part):
     return uploaded_image(img)
 
 
+@register.simple_tag()
+def part_parameter(part: Part, parameter_name: str):
+    """Return a PartParameter object for the given part and parameter name
+
+    Arguments:
+        part: A Part object
+        parameter_name: The name of the parameter to retrieve
+
+    Returns:
+        A PartParameter object, or None if not found
+    """
+    if type(part) is Part:
+        return part.get_parameter(parameter_name)
+    else:
+        return None
+
+
 @register.simple_tag()
 def company_image(company):
     """Return a fully-qualified path for a company image.

docs/docs/report/helpers.md

@@ -224,3 +224,31 @@ You can add asset images to the reports and labels by using the `{% raw %}{% ass
 <img src="{% asset 'my_awesome_logo.png' %}"/>
 {% endraw %}
 ```
+
+## Part Parameters
+
+If you need to load a part parameter for a particular Part, within the context of your template, you can use the `part_parameter` template tag.
+
+The following example assumes that you have a report or label which contains a valid [Part](../part/part.md) instance:
+
+```
+{% raw %}
+{% load report %}
+
+{% part_parameter part "length" as length %}
+
+Part: {{ part.name }}<br>
+Length: {{ length.data }} [{{ length.units }}]
+
+{% endraw %}
+```
+
+A [Part Parameter](../part/parameter.md) has the following available attributes:
+
+| Attribute | Description |
+| --- | --- |
+| Name | The *name* of the parameter (e.g. "Length") |
+| Description | The *description* of the parameter |
+| Data | The *value* of the parameter (e.g. "123.4") |
+| Units | The *units* of the parameter (e.g. "km") |
+| Template | A reference to a [PartParameterTemplate](../part/parameter.md#parameter-templates) |

docs/docs/report/labels/part_labels.md

@@ -34,9 +34,9 @@ The following context variables are made available to the Part label template:
 | qr_data | String data which can be rendered to a QR code |
 | parameters | Map (Python dictionary) object containing the parameters associated with the part instance |
 
-#### Parameters
+#### Parameter Values
 
-The part parameters can be accessed by parameter name lookup in the template, as follows:
+The part parameter *values* can be accessed by parameter name lookup in the template, as follows:
 
 ```html
 {% raw %}
@@ -47,7 +47,8 @@ Length: {{ parameters.length }}
 {% endraw %}
 ```
 
-Note that for parameters which include a `space` character in their name, lookup using the "dot" notation won't work! In this case, try using the [key lookup](../helpers.md#key-access) method:
+!!! warning "Spaces"
+    Note that for parameters which include a `space` character in their name, lookup using the "dot" notation won't work! In this case, try using the [key lookup](../helpers.md#key-access) method:
 
 ```html
 {% raw %}
@@ -55,3 +56,36 @@ Note that for parameters which include a `space` character in their name, lookup
 Voltage Rating: {% getkey parameters "Voltage Rating" %}
 {% endraw %}
 ```
+
+#### Parameter Data
+
+If you require access to the parameter data itself, and not just the "value" of a particular parameter, you can use the `part_parameter` [helper function](../helpers.md#part-parameters).
+
+For example, the following label template can be used to generate a label which contains parameter data in addition to parameter units:
+
+```html
+{% raw %}
+{% extends "label/label_base.html" %}
+
+{% load report %}
+
+{% block content %}
+
+{% part_parameter part "Width" as width %}
+{% part_parameter part "Length" as length %}
+
+<div>
+    Part: {{ part.full_name }}<br>
+    Width: {{ width.data }} [{{ width.units }}]<br>
+    Length: {{ length.data }} [{{ length.units }}]
+</div>
+
+{% endblock content %}
+{% endraw %}
+```
+
+The following label is produced:
+
+{% with id="report-parameters", url="report/label_with_parameters.png", description="Label with parameters" %}
+{% include 'img.html' %}
+{% endwith %}