Assert

The Assert function tests a condition and aborts the script if the condition tests false. This function mimics the common C and C++ ASSERT or assert macros.

Syntax

Assert( condition )

Assert( condition, message )

where

condition is an expression that produces a result.

message is optional, and is displayed if condition fails.

The condition can be any condition that produces a value that can be tested. For example, if testing a numeric expression, the Assert will exit the script if the expression evaluates false, numeric zero, or nil. The table below lists the conditions that cause failure.

Assert Expression Failure Conditions

Expression result:	Failure condition:
number	0
string	nil or 0-length
table	nil (non existent)
boolean	false
C pointer	NULL
CFunction	nil (non existent)
Lua thread	nil
userdata	nil (non existent)
nil	always

Example

The following condition fails the Assert test and exits the script if fewer than 2 images were loaded.


V = LoadImages(2)	-- load 2 images and create a CImageView
Assert( V:Count() < 2 )	-- fails without a message if 2 images were not loaded