Data types
Overview
In Qodly, data are handled according to their type in two places: the datastore and the QodlyScript language.
Although they are usually equivalent, some data types available at the datastore level are not directly available in the language and are automatically converted. Conversely, some data types can only be handled through the language. The following table lists all available data types and how they are supported/declared:
Data Types | Variable declaration | Datastore support (type) | Default value |
---|---|---|---|
blob | var blob | blob | 0 byte |
var 4D.Blob | object | null | |
boolean | var boolean | bool | false |
collection | var collection | - | null |
date | var date | date | 00-00-00 |
null | - | - | null |
number | var integer , var number | number | 0 |
object | var object | object | null |
picture | var picture | image | pictureSize == 0 |
string | var string | string | "" |
time | var time | duration | 00:00:00 |
undefined | - | - | undefined |
variant | var variant | - | undefined |
Variant is actually not a data type but a variable type that can contain a value of any other data type.
type
type ( var : any ) : integer
Parameter | Type | Description | |
---|---|---|---|
var | any | → | Variable to be tested |
Result | integer | ← | Data type number |
Description
The type
command returns a numeric value that indicates the type of variable you have passed in the var parameter.
Qodly provides the following predefined constants:
Constant | Value |
---|---|
kBlob | 30 |
kBoolean | 6 |
kCollection | 42 |
kDate | 4 |
kInteger | 9 |
kNull | 255 |
kObject | 38 |
kPicture | 3 |
kNumber | 1 |
kString | 2 |
kTime | 11 |
kUndefined | 5 |
kVariant | 12 |
You can apply the type
function to variables and sequential parameters ($1, $2...) of a method.
You cannot apply the type
function to scalar expressions such as object properties (emp.name) or collection elements (myColl[5]). To do this, you must use the valueType
command.
valueType
valueType ( expression : any ) : integer
Parameter | Type | Description | |
---|---|---|---|
expression | any | → | Expression whose resulting value to be tested |
Result | integer | ← | Data type number |
Description
The valueType
command returns the type of the value resulting from the evaluation of the expression you passed as parameter.
The command returns a numeric value that can be compared with one of the following constants provided by Qodly:
Constant | Value |
---|---|
kBlob | 30 |
kBoolean | 6 |
kCollection | 42 |
kDate | 4 |
kInteger | 9 |
kNull | 255 |
kObject | 38 |
kPicture | 3 |
kNumber | 1 |
kString | 2 |
kTime | 11 |
kUndefined | 5 |
kVariant | 12 |
This command is designed to return the type of a scalar expression, i.e. the value stored in or returned by the expression parameter. In particular, it can be applied to the following Qodly expressions:
- object properties (emp.name),
- collection elements (myCol[5]).
Numerical object properties are always considered number values:
var o : object
var vType : integer
o = newObject("value",42)
vType = valueType(o.value) //vType = kNumber
Example 1
You want to handle the various possible types of an object property value:
switch
:(valueType(o.value) == kNumber)
//handle a numeric value
:(valueType(o.value) == kString)
//handle a string
:(valueType(o.value) == kObject)
//handle a sub-object
...
end
Example 2
You want to sum up all numeric values in a collection:
var col : collection
var colSum : number
col = newCollection("Hello",20,"World2",15,50,currentDate,true,10)
for(i,0,col.length-1) //-1 since collections start at 0
if(valueType(col[i]) == kNumber)
colSum = colSum+col[i]
end
end
Converting data types
QodlyScript contains operators and commands to convert between data types, where such conversions are meaningful. QodlyScript enforces data type checking. For example, you cannot write: "abc"+0.5+!12/25/96!-?00:30:45?. This will generate syntax errors.
The following table lists the basic data types, the data types to which they can be converted, and the commands used to do so:
Data Type to Convert | to String | to Number | to Date | to Time | to Boolean |
---|---|---|---|---|---|
String (1) | num | date | time | bool | |
Number (2) | string | bool | |||
Date | string | bool | |||
Time | string | bool | |||
Boolean | num |
(1) Strings formatted in JSON can be converted into scalar data, objects, or collections using the jsonParse
command.
(2) Time values are durations and can be treated as numbers.
In addition to the data conversions listed in this table, more sophisticated data conversions can be obtained by combining operators and other commands.