Delphi pitfalls: Enumerated types and for loops

Not all for loops are created equal.

for x in [value1, value2, value3]

You would expect to see x vary in the order of the values in the list.

However – if x and the values are of an enumerated type, looping the “list”
does NOT loop in the apparent order of the constant, but in the order of the enumerated type declaration, such as it would for any set.

An example:

The above code yields

Declared: TEnum = (plough, foo, bar, wtf)
Test order: [wtf, plough, bar, foo]

Looping an Enum Set

Looping an Enum Array

Press Enter:

This can be easy to miss, so if loop order is important – make sure you code your enums into an actual array and do not leave them as a set.

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