Enable multiple quantity measurements per log

Problem/Motivation

The "Quantity" field is a field collection with two sub-fields: "Value" (fraction field) and "Units" (taxonomy term reference field), which is available on many log types in farmOS.

Currently, Quantity field instances only allow a single quantity to be entered.

It is very easy to allow multiple quantities, simply by changing the field instance's "Number of values" setting to "Unlimited". This will allow users to click "Add another" to add multiple quantities to a log.

However, with only "Value" and "Units" as sub-fields, there is no clear way to differentiate the different quantities entered. Intuitively it may be possible, but not programatically.

Proposed resolution

The proposed resolution is to add two additional sub-fields to the Quantity field collection, in addition to making it a multi-value field:

• Measure - A dropdown list of specific forms of measurement (Count, Length, Weight, etc)
• Label - An arbitrary textfield that allows the quantity measurement to be labelled, for further differentiation

Both of these sub-fields would be optional. The "Units" field would also be made optional - so it will be up to the user to decide which fields they need for a proper measurement. This will allow a lot of flexibility in data capture.

Below is the initial list of "Measure" options that we will start with. More can be identified/added in the future.

• Count
• Length
• Weight
• Volume
• Time
• Temperature
• Water content
• Value
• Rating
• Ratio
• Probability

Remaining tasks

• Add a Measure field to Quantities.
• Add a function that defines the available options for the Measure field.
• Update Quantity field instance descriptions to include Measure.
• Add a Label field to Quantities.
• Allow multiple quantities to be entered on each log. Hide initial form and require user to add first item.
• Make "Units" field not required.
• ...

User interface changes

• New Quantity sub-fields: Measure and Label
• Click "Add additional item" to add Quantity field collections to logs.

API changes

None

Data model changes

• New Quantity sub-fields: Measure and Label