Using expressions

Using expressions

Introduction

For some entity type attributes an expression can be set that determines whether or not a condition is true based on the attribute values e.g. to determine whether values are valid. The expression format is based on the Magma JavaScript API.

Examples

The following expression returns true when the value of attribute 'myAttributeName' of an entity only contains alphanumberic characters:

$('myStringAttributeName').matches(/^[a-z0-9]+$/i).value()

In this example:

• '$(...)' is the selector

• 'myStringAttributeName' is an attribute name

• 'matches' is a chaining operation

• 'value' is a terminal operation

Chaining operations allows you to express complex expressions:

$('myIntAttributeName').gt(3).and($('myIntAttributeName').lt(6)).value()

Chaining operations

Numerical operations

Operator	Parameters	Example	Description
plus	Number	$('height').plus(100).value()	height + 100
pow	Number	$('height').pow(100).value()	height ^ 100
times	Number	$('height').times(100).value()	height * 100
div	Number	$('height').div(100).value()	height / 100
gt	Number	$('height').gt(100).value()	height > 100
lt	Number	$('height').lt(100).value()	height < 100
ge	Number	$('height').ge(100).value()	height >= 100
le	Number	$('height').le(100).value()	height <= 100

Binary operations

Operator	Parameters	Example	Description
eq	Number	$('height').eq(100).value()	height === 100
matches	Regex	$('name').matches(/^[a-z0-9]+$/i).value()	name is alphanumerical
isNull	-	$('height').isNull().value()	height === null
not	-	$('hasEars').not().value()	!hasEars
or	Expression	$('male').or($('female')).value()	male		female
and	Expression	$('female').and($('pregnant')).value()	female && pregnant

Unit operations

Operator	Parameters	Example	Description
unit	Unit	$('height').unit('cm')	Sets the current value unit to cm
toUnit	Unit	$('height').unit('m').toUnit('cm').value()	Converts the current value based on the change in units

Other

Operator	Parameters	Example	Description
age	-	$('dateOfBirth').age().value()	Returns the age based on the date of birth and the current year
map	Object	$('data').map({0:1, 1:2}).value()	Maps categories to each other
group	Array	$('age').group([18, 35, 50, 75]).value()	Produces left-inclusive ranges with the given boundaries, i.e. (-∞, 18), [18, 35), [35, 50), [50, 75), [75, +∞) and then returns the interval that the attribute value is in, i.el '18-35'
attr	String	$('person').attr('name').value()	Returns the value of an attribute of a reference

Terminal operations

Operator	Parameters	Example	Description
value	-	$('height').value()	JavaScript value

Special case: reference types

If an attribute is a reference type (MREF, XREF, CATEGORICAL, CATEGORICAL_MREF) you can use the 'attr' operation, to access the values of different columns in the row being referenced. E.g. $('cookie').attr('name').value() gives you the value of the name column inside the table being referenced by the cookie column. See below for a more detailed example.

Imagine table A referencing table B.

Table A has 2 columns: id, cookie. Table B has 3 columns: id, name, tastiness.

The cookie column in table A references table B.

Table A

id	cookie
A	1

Table B

id	name	tastiness
1	Chocolate chip	9/10

Expressions allow you to do the following

// Expressions are based on table A

$('cookie').value() // results in '1'
$('cookie').attr('id').value() // results in '1'
$('cookie').attr('name').value() // results in 'Chocolate chip'
$('cookie').attr('tastiness').value() // results in '9/10'

In the following case, we have Table A which has multiple references to Table B e.g. an MREF

Table A

id	cookie
A	1,2,3

Table B

id	name	tastiness
1	Chocolate chip	9/10
2	Strawberry cookie	10/10
3	Banana cookie	7/10

// Expressions are based on table A

$('cookies').map(function (cookie) {
    // Pick one of the following
    return cookie.value()                   // results in ['1', '2', '3']
    return cookie.attr('id').value()        // results in ['1', '2', '3']
    return cookie.attr('name').value()      // results in ['Chocolate chip', 'Strawberry cookie', 'Banana cookie']
    return cookie.attr('tastiness').value() // results in ['9/10', '10/10', '7/10']
}).value()