Archicad 29 IFS Function: A Guide to Condition Order and Default Results

The IFS function described in Archicad 29 help documentation evaluates multiple logical conditions in order and returns the value associated with the first true condition. This guide explains the function’s syntax and what to keep in mind when writing conditions, with examples. Graphisoft’s Archicad 26 Property Manager documentation provides separate information about managing project properties and data types. The two documents cover different topics and versions; this guide does not assume that IFS works with expression-based properties.

How does the IFS function work?

IFS can be used instead of multiple nested IF statements. You provide the function with conditions and the values associated with them. The conditions are checked in order, and the value for the first true condition is returned as the result. This makes the order of the conditions important: if an earlier condition is true, the function will not reach the later ones.

The example in Archicad help groups beams into three categories based on their length. If the left-side length is greater than 600 cm, the result is “Long”; if it is less than 200 cm, the result is “Short.” “Medium” is used as the default result for beams that meet neither condition:

IFS (Length Left > 600 cm, "Long", Length Left < 200 cm, "Short", TRUE, "Medium")

Here, Length Left refers to the length of the beam’s left side. The source documentation explains that the “left” and “right” sides are determined relative to the beam’s reference axis, and the axis direction is determined by the direction in which the cursor is dragged while drawing the beam. In the example, lengths that meet neither of the two boundary conditions return “Medium.”

IFS accepts up to 127 logical conditions. The character used to separate the function’s arguments can be a comma or a semicolon; according to Graphisoft, the separator used depends on the computer’s regional settings.

Preparing conditions: step by step

1. Define the result categories. Decide in advance which value you want returned for each condition. In the beam example, these values are the text strings “Long,” “Short,” and “Medium.” All result values in the function must have the same data type and units.

2. Put the conditions in order. Because IFS returns a result at the first true condition, the order of the tests affects the output. In the example, lengths greater than 600 cm are checked first, followed by lengths below 200 cm; a default result is defined for all remaining cases. For your own use, decide which condition should be evaluated first.

3. Pair each condition with its corresponding value. The syntax is IFS (Logical1, Value1, [Logical2, Value2]...). The logical part evaluates to true or false; the value that follows each logical condition is returned when that condition is true. The source states that up to 127 logical conditions can be defined.

4. Decide on a default result. If no condition is true and no default value has been defined, the result is Undefined. If you want every possible case to return a value, you can add TRUE as the final logical condition, followed by a default value. This value must also have the same data type as the other results.

5. Check the separator and result types. Depending on the regional settings of the environment where you use the expression, you may need a comma or a semicolon. Also review the results to confirm that they all meet the same data type and units requirements. Archicad’s documentation says the separator is determined automatically based on the regional settings.

Distinguishing the Property Manager documentation

The Archicad 26 Property Manager documentation describes how to create properties and specify their data types. You can access this window via Options > Property Manager or through the Classification Manager. The documentation lists data types for properties such as String, Number, Integer, Area, Length, Angle, Volume, Tags List, Option Set, and True/False. This information is a separate reference for anyone managing project properties; it does not show that IFS can be used with those properties.

The documentation states that Tags List and Option Set types cannot be used as expression-based properties. An Option Set with multiple selection disabled, however, can be used inside an expression. These are rules concerning property types in Property Manager. They should not be confused with the requirement that IFS results have the same data type and units; conclusions should remain within the limits confirmed by the sources. Also note that the Property Manager information comes from Archicad 26, while the IFS explanation is from the Archicad 29 help page.

What does this mean for architecture and visualization workflows?

By evaluating conditions in sequence within a single function, IFS demonstrates how classifications based on multiple conditions can be expressed. The documentation’s example of classifying beam lengths illustrates how different results can be defined according to the dimensions of project elements. Architecture and interior design teams can use the example to understand condition order and the idea of a default result; however, the information here does not provide a verified guide to applying IFS to another property field.

The sources provide no information about hardware requirements, render time impact, licensing terms, or compatibility with other software for IFS. Any practical assessment of the function should therefore be limited to its documented behavior and syntax. In particular, keep the version distinction in mind: the IFS explanation is from Archicad 29, while the Property Manager information is from Archicad 26.

Common mistakes

• Ignoring condition order: Since the result for the first true condition is returned, write conditions in the order of priority you intend.

• Forgetting the default result: If no condition is true and there is no default result, Undefined is returned.

• Mixing result types: All IFS results must meet the same data type and units requirements.

• Choosing the wrong separator: A comma or semicolon may be required, depending on the computer’s regional settings.

• Treating separate documents as proof of a single workflow: The Property Manager and IFS documentation covers different versions and topics; it does not confirm that they can be used together.