bcquality/custom/knowledge/style/binary-choice-must-be-boolean.md

bc-version	domain	keywords	technologies	countries	application-area
all	style	boolean option yes-no magic-number variable-typing field-typing	al	w1	all

Binary yes/no choices must be typed as Boolean, not Option or Integer

Description

When a field or variable represents exactly two states — yes/no, on/off, active/inactive, blocked/not blocked — it must be typed Boolean. Modeling that same two-state choice as an Option/Enum with two members, or as an Integer with two magic-number values (0/1), adds a layer of indirection a reader has to resolve before understanding the code, and it invites a three-way branch (if X = 0 then ... else if X = 1 then ...) where a simple if X then ... would do.

This is distinct from a genuine multi-value choice — see fixed-choice-set-must-use-enum-not-integer — where more than two named states legitimately call for Enum. The line is the state count: exactly two mutually exclusive states is a Boolean question, not an enumeration.

Best Practice

field(50; Blocked; Boolean)
{
}

var
    IsOverdue: Boolean;
...
IsOverdue := DueDate < Today;
if IsOverdue then
    ...

Anti Pattern

field(50; Status; Option)
{
    OptionMembers = Active,Blocked;
}

var
    OverdueFlag: Integer; // 0 = No, 1 = Yes
...
if OverdueFlag = 1 then
    ...

An Option/Integer standing in for a true yes/no forces every caller to remember which value means what, and it leaves room for a third, meaningless value that a Boolean cannot represent.