How to check existence of a sql server object and drop it?

Question

EDIT: the function creation was missing, sorry about that

I have a T-SQL request that goes:

DECLARE @IsSomething bit
SET @IsSomething = 0
IF /some tests/ SET @IsSomething = 1
EXEC('
CREATE FUNCTION IsSomething ()
RETURNS bit
AS
BEGIN
    RETURN ' + @IsSomething + '
END')

Of course if I run it twice I get

There is already an object named 'IsSomething ' in the database. 

How would I do something like this:

IF EXIST @IsSomething DESTROY @IsSomething // (Pseudo bad code)

Answer 1

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id (N'[dbo].[IsSomething]') AND OBJECTPROPERTY(id, N'IsFunction') = 1) 

DROP function IsSomething
GO