The "Set variable" action and data types

In Power Automate Desktop, you add actions by dragging and dropping them in the GUI, but internally, flows are built in a programming language called Robin.

When you create actions, you often see parameters enclosed in percent signs (%), and you can put expressions, objects, and more inside them.

This article explains the data types you can define with the “Set variable” action.

Define variablesExplains how to define variables, which you can use to hold and output values in a flow.

Define string and number data

First, let’s look at what happens when you enter a value in the “Value” field without enclosing it in percent signs.

In this case, the Numeric value type is assigned automatically if the value contains only digits, and the Text value type is assigned if it contains anything else.

Copy the following code and paste it into the flow designer.

This creates a flow that defines two variables: a string and a number.

SET VarNumber TO 15000
SET VarString TO $'''Hello'''

When you run the flow and check the flow variables, you can see that they were automatically identified as “Numeric value” and “Text value”, respectively.

Define lists and objects

Next, let’s look at what happens when you enclose the value in percent signs.

In this case, you can define not only numbers and strings but also lists (arrays) and objects with multiple properties, all with this one action.

Copy the following code and paste it into the flow designer.

This creates a flow that defines two variables: a list and an object.

SET InitializedList TO ['itemA', 'itemB', 'itemC']
SET InitializedObject TO { 'prop': 'value', 'array': ['itemA', 'itemB'] }

When you run the flow and check the flow variables, you can see that the data types differ from the previous example: they are “List” and “Custom object”, respectively.

You can also define a Boolean variable by entering %True% or %False% in the “Value” field.

Set multiple initial values in a listWhen you need to define a list and put several initial values in it, building the flow by combining "Create new list" and "Add item to list" makes the flow longer as the number of items grows.

Define a variable with multiple propertiesThere's no ready-made action for this, but with a little ingenuity, you can define a variable with multiple properties in a single action.

Can you define a date type?

The short answer is yes.

If you enter d followed by a date in double quotation marks in the “Value” field, such as %d"2022-03-25"%, a date (Datetime) value is assigned. To include the time as well, use the format %d"yyyy-MM-dd HH:mm:ss.ff+zzz"%.

If you want to get the current date and time, use the “Get current date and time” action.