CodeCop Warning AA0150

Article
02/26/2024

Do not declare parameters by reference if their values are never changed.

Description

Do not declare parameters by reference if their values are never changed.

Reason for the rule

Defining a parameter as passed by reference and not actually changing it may lead to an unexpected variable value if the variable is later changed in the method. In addition, other developers may think that the value is changed in the method, eventhough that is not true.

Bad code example 1

The following example illustrates the developer's error - forgot to remove var property of MyList in Method1, after redesigning Method2.

procedure Method1(var MyB: boolean)
begin
Method2(MyB);
end;

procedure Method2(MyC: boolean)
var
someVar: boolean;
begin
someVar := MyC;
end;

Good code example 1

procedure Method1(MyB: boolean)
begin
Method2(MyB);
end;

procedure Method2(MyC: boolean)
var
someVar: boolean;
begin
someVar := MyC;
end;

Bad code example 2

procedure Method1(var InvtValue: array[5] of Integer)
var 
MyInt: Integer;
begin
MyInt := InvtValue[0];
end;

Good code example 2

procedure Method1(InvtValue: array[5] of Integer)
var 
MyInt: Integer;
begin
MyInt := InvtValue[0];
end;

Remarks

Variables of the following types are analyzed: Integer, BigInteger, Boolean, Byte, Char, Code, Date, DateTime, Decimal, Time, and Text. Also lists and arrays of above types are analyzed - these types should be changed with appropriate methods if they are passed by reference.

Event subscribers, Integration Events, and ConfirmHanders are also not analyzed. Parameters of the type List can be also changed following built-in methods: Add, AddRange, Set, Insert, Remove, RemoveAt, RemoveRange, Reverse. Arrays additionally changed by CompressArray and CopyArray. Also the Evaluate built-in method is supported.