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()