Type Conversion

Template Engine will try to automatically convert the input data value to the expected data type.

Conversion Rules

For some data types, values can be automatically converted following the rules:

Numbers

If Number is expected, values of other data types can be converted as follows:

Source	Number Representative
Null Reference (null)	0
Undefined	0
Boolean	1 for true, 0 for false
String	Will try to parse the number in the string
DateTime	Will convert to timestamp

Boolean

If Boolean is expected, values of other data types can be converted as follows:

Source	Boolean Representative
Null Reference (null)	false
Undefined	false
String	false if empty, true otherwise
List or Map	false if empty, true otherwise
Number	false for 0, true otherwise

String

If String is expected, values of other data types will be converted to string to the same form as it would print it using output code island.

DateTime

If DateTime is expected, values of other data types can be converted as follows:

Source	DateTime Representative
String	Will try to parse the ISO 8601 string: yyyy-MM-dd'T'HH:mm:ss.SSSZ If string is now, will be converted to current datetime.
Number	Will convert to date using this number as Unix timestamp

Where it works?

Automatic data type conversion is available for:

• Operators and Expressions;
• if constructs;
• Functions arguments;
• Methods parameters with some exceptions and special behavior.

Data Type Conversion in Methods Parameters

• Doesn't work for some list and map methods.
• If a method parameter is documented with multiple data types (so-called overloads), the template engine will attempt to convert them in the order specified there.

Comparison Operations

Binary Comparison Operators (>, >=, <, <=, in, ==, !=) use the following algorithm:

1. If both operands can be converted to a numbers, they are converted and compared as numbers;
2. If at least one of the operands cannot be converted to a number, both operands are converted to strings and compared as strings.

This algorithm is universal, but in some cases the order of operations should be taken into account. For example:

{{ 'true' == 1 == true }}
{{ true == 1 == 'true' }}

It would seem that both expressions should print true, but the first one prints false.

First expression:

1. 'true' == 1 evaluates as false, because string 'true' cannot be converted to a number, so both operands are converted to strings and compared as 'true' and '1' that gives false in result;
2. Second operation becomes false == true that gives false as the final result of the whole expression.

Second expression:

1. true == 1 evaluates as true, because boolean true can be converted to number 1, so both operands are compared as numbers (they are equal);
2. Second operation becomes true == 'true' that gives true as the final result of the whole expression, but only because second operand 'true' is string that cannot be converted to a number, so both operands are converted to strings and compared as 'true' and 'true' (they are equal).