Creating and Deleting Structs

Structs are created using the $newstruct ProcScript function, but they can also be created implicitly. They are removed when there is no longer a parameter or variable that refers to them.

To create Structs, you can:

Creating Structs

  1. Use the ProcScript function $newstruct to explicitly create a new, empty Struct.
    vStruct = $newstruct
  2. Assign a value to a struct variable or parameter.
    vStruct1->title = "Users Guide"

    vStruct now points to a newly created Struct with member title.

    For more information, see Assigning Values to Structs.

  3. Assign a value to an allowed Struct function ($name, $index, $parent, or $scalar) or to the $tags Struct.
    vStruct2->$name = "My Book"

    vStruct2 created and assigned a name.

  4. Use one of the conversion functions to transform a complex data structure, such as XML, or a Uniface entity to a Struct.
      xmlstream pXml: in
      struct pStruct: out
    xmlToStruct pStruct, pXml

    pStruct now points to a (top level) Struct .

  5. Assign an existing Struct to the member of another existing Struct.
    xmlToStruct pStruct1, pXml  
    vStruct2->memberX = pStruct1     

    memberX is a new Struct, which is a copy of pStruct1

  6. To create or update a Struct member, assign a member to an existing Struct.

    If the named Struct exists, it is updated. If it does not, it is created.

      struct vStruct1
      struct vStruct2
    xmlToStruct vStruct1, pXml                     ; Create vStruct1 
    vStruct1->complexMemberX->memberY = 1         ; Create/update a scalar member
    vStruct1->complexMemberX->memberZ = vStruct2  ; Create/update a struct member

Deleting Structs and Members

To delete a Struct, you need to ensure that there are no variables or parameters that refer to it. There is no ProcScript statement to delete a Struct. For local variables, this automatically happens when the entry or operation completes.

The best way to explicitly remove a Struct is to assign an empty value to the struct variable that refers to a Struct.

Example: Assign a new value to the Struct variable that refers to the Struct.

  struct vStruct1, vStruct2

vStruct1 = $newstruct
vStruct1->x = "member x"

vStruct2 now has no members called x.

Note:  When a Struct variable is declared, it is implicitly initialized to Null, so assigning such a Struct variable to an existing Struct variable removes the original Struct. For more information, see Null Values.

Creating and Building a Struct

  struct vStruct, vStructCollection
  string vNames

    vNames = "John ;Mary ;Jane"
    while (vNames != "")
        vStruct = $newstruct               ;- Create an empty Struct
        vStruct->name = $itemnr(1, vNames)
        vStructCollection->*{-1} = vStruct ;- append to collection
        delitem vNames, 1
    vStructCollection->$name = "people"
    putmess vStructCollection->$dbgstring  ;- display result in message frame

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