OB Get

OB Get ( object ; property {; type} ) : Expression

Parameter	Type		Description
object	Object, Object	→	Structured object
property	Text	→	Name of property to read
type	Integer	→	Type to which to convert the value
Function result	Expression	←	Current value of property

Description

The OB Get command returns the current value of the property of the object, optionally converted into the type specified.

object can be an object varialble or a 4D object field.

Note: This command supports attribute definitions in 4D Write Pro objects, like the WP GET ATTRIBUTES command (see example 9).

In the property parameter, pass the label of the property to be read. Note that the property parameter is case sensitive.

By default, 4D returns the value of the property in its original type. You can "force" the typing of the value returned using the optional type parameter. To do this, in type you pass one of the following constants found in the Field and Variable Types theme:

Constant	Type	Value
Is Boolean	Integer	6
Is collection	Integer	42
Is date	Integer	4
Is longint	Integer	9
Is null	Integer	255
Is object	Integer	38
Is picture	Integer	3
Is pointer	Integer	23
Is real	Integer	1
Is text	Integer	2
Is time	Integer	11

The command returns the value of the property. Several types of data are supported. Note that:

• a pointer is returned as such; it can be evaluated using the JSON Stringify command.
• depending on your database date settings, dates in object attributes are stored either with date type or text type (starting with 4D v16 R6). For more information, please refer to the "Use date type instead of ISO date format in objects" option in the Compatibility page. In order for OB Get to correctly interpret a date stored as a text, you need to use the Is date constant (see example 5).
• in real values, the decimal separator is always a period "."
• times are returned as a number. Times are stored in seconds by default in objects (see compatibility note below). Use the Is time constant to get a 4D formatted time value.

Compatibility Notes:

• In versions prior to v17, times were stored in milliseconds inside objects. For compatibility needs, this previous behavior can be restored using the Times inside objects selector of the SET DATABASE PARAMETER command. Whatever the setting, the result will be correct when the Is time constant is passed.
• (4D Write Pro) In versions prior to v16 R6, when property defined a 4D Write Pro image attribute (such as wk image), a text value containing a data URI was always returned. Starting with 4D v16 R6, 4D Write Pro image attributes are always returned as picture values. You must use a specific property like wk image url to get a data URI.
• In versions prior to v16 R4, when property contains a null value and if the type parameter is not used, 4D returns an empty string. For 4D v16 R4 and higher versions, the Is null constant is returned in this case. To preserve compatibilty, this change takes effect only if the "Use object notation to access objects properties (Unicode required)" option is enabled in the database (see the Compatibility page).

Example 1

Retrieving a text type value:

 var $ref : Object
 var $FirstName : Text
 OB SET($ref;"FirstName";"Harry")
 $FirstName:=OB Get($ref;"FirstName") // $FirstName = "Harry" (text)

Example 2

Retrieving a real number value converted into a longint:

 OB SET($ref ;"age";42)
 $age:=OB Get($ref ;"age") // $age is a real number (default)
 $age:=OB Get($ref ;"age";Is longint) // $age is a longint

Example 3

Retrieving the values of an object:

 var $ref1;$ref2 : Object
 OB SET($ref1;"LastName";"Smith") // $ref1={"LastName":"Smith"}
 OB SET($ref2;"son";$ref1) // $ref2={"son":{"LastName":"Smith"}}
 $son:=OB Get($ref2;"son") // $son={"LastName":"john"} (object)
 $sonsName:=OB Get($son ;"name") // $sonsName="john" (text)

Example 4

Modifying the age of an employee twice:

 var $ref_john;$ref_jim : Object
 OB SET($ref_john;"name";"John";"age";35)
 OB SET($ref_jim;"name";"Jim";"age";40)
 APPEND TO ARRAY($myArray;$ref_john) // we create an object array
 APPEND TO ARRAY($myArray;$ref_jim)
  // we change the age for John from 35 to 25
 OB SET($myArray{1};"age";25)
  // We replace the age of "John" in the array
 For($i;1;Size of array($myArray))
    If(OB Get($myArray{$i};"name")="John")
       OB SET($myArray{$i};"age";36) // instead of 25
  // $ref_john={"name":"John","age":36}
    End if
 End for

Example 5

When retrieving a date, the resulting value depends on the current database date settings.

• If the "Use date type instead of ISO date format in objects" option is not checked:

 var $object : Object
 var $birthday : Date
 var $birthdayString : Text
 OB SET($object;"Birthday";!30/01/2010!)
 $birthday:=OB Get($object;"Birthday";Is date) //30/01/10
 $birthdayString:=OB Get($object;"Birthday") //"2010-01-29T23:00:00.000Z" (Paris time zone)

• If the "Use date type instead of ISO date format in objects" option is checked:

 var $object : Object
 var $birthday : Date
 OB SET($object;"Birthday";!30/01/2010!)
 $birthday:=OB Get($object;"Birthday") //30/01/10, no need for Is date

Note: For more information on this setting, please refer to the Compatibility page.

Example 6

Using nested objects:

 var $ref1;$child;$children : Object
 var $childName : Text
 OB SET($ref1;"firstname";"John";"lastname";"Monroe")
  //{"firstname":"john","lastname";"Monroe"}
 OB SET($children;"children";$ref1)
 $child:=OB Get($children;"children")
  //$son = {"firstname":"John","lastname":"Monroe"} (object)
 $childName:=OB Get($child;"lastname")
  //$childName = "Monroe" (text)
  //or
 $childName:=OB Get(OB Get($children;"children");"lastname")
  // $childName = "Monroe" (text)

Example 7

Recovery in 4D of a time stored in an object:

 var $obj_o : Object
 var $set_h;$get_h : Time
 
 $set_h:=?01:00:00?+1
 OB SET($obj_o;"myHour";$set_h)
  // $obj_o = {"myHour":3601}
  // The time is stored in seconds
 $get_h:=OB Get($obj_o;"myHour";Is time)
  // $get_h = ?01:00:01?

Example 8

Examples of working with 4D object fields:

  // Define a value
 OB SET([People]Identity_OB;"First name";$firstName)
 OB SET([People]Identity_OB;"Last name";$lastName)
 
  // Get a value
 $firstName:=OB Get([People]Identity_OB;"First name")
 $lastName:=OB Get([People]Identity_OB;"Last name")

Example 9

In the method of a form containing a 4D Write Pro area, you can write:

 If(FORM Event=On Validate)
    OB SET([MyDocuments]My4DWP;"myatt_Last edition by";Current user)
    OB SET([MyDocuments]My4DWP;"myatt_Category";"Memo")
 End if

You can also read custom attributes of the documents:

 vAttrib:=OB Get([MyDocuments]My4DWP;"myatt_Last edition by")

Example 10

You want to know the size of a picture stored in an object attribute:

 var $vSize : Integer
 $vSize:=Picture size(OB Get($object;"photo";Is picture))

Note: If you assign the result of the command to a picture variable, the Is picture constant is not necessary. Example:

 var $vPict : Picture
 $vPict:=OB Get($object;"photo") //"is picture" is useless in this case

See also

Field and Variable Types
OB Copy
OB SET