Pseudo-Objects in Active Server Pages

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' Entity.inc -- Functions and subroutines for Entity pseudo-objects.

' Entity_New() creates a new Entity.
'
function Entity_New()
   dim obj
   dim fields
   dim defaults
   dim i

   ' Create the empty object.

   set obj = Server.CreateObject("Scripting.Dictionary")

   ' Add the base fields.

   obj.Add "_Table",      ""
   obj.Add "_PrimaryKey", ""

   set Entity_New = obj
end function

' Entity_Load() loads a list of objects from the database.
'
function Entity_Load(strConn, emptyObj, fields, where, orderBy)
   dim list
   dim recordset
   dim obj
   dim fieldNames
   dim value
   dim key
   dim i
   
   ' Get field names.
   
   fieldNames = emptyObj.Keys()

   ' Create the list and run the query.

   set list = Server.CreateObject("Scripting.Dictionary")
   set recordset = DB_Query(strConn, fields, emptyObj("_Table"), _
      where, orderBy)

   ' Load the records into the list.

   do while not recordset.EOF
      set obj = Entity_Clone(emptyObj)
      
      for i = 0 to UBound(fieldNames)
         if Left(fieldNames(i), 1) <> "_" then
            value = Entity_ConvertType( _
               DB_NullVal( _
                  recordset(fieldNames(i)).Value, emptyObj(fieldNames(i))), _
                  TypeName(obj(fieldNames(i))) )
            obj(fieldNames(i)) = value
         end if
      next
      
      ' Add the object to the list.
      
      key = recordset(emptyObj("_PrimaryKey")).Value
      
      if TypeName(key) <> "String" then
         key = CStr(key)
      end if
      
      list.Add key, obj
      
      ' Move to the next record.

      recordset.MoveNext
   loop

   ' Close the recordset.

   recordset.Close

   ' Return the list.

   set Entity_Load = list
end function
     
' Entity_Insert() inserts the given object into the database.
'
function Entity_Insert(strConn, obj)
   dim fields
   dim values
   dim keys
   dim data
   dim i
   
   ' Build the fields and values clauses.
   
   fields = ""
   values = ""
   keys = obj.Keys()

   for i = 0 to UBound(keys)
      
      ' If not an internal key ...
      
      if Left(keys(i), 1) <> "_" then

         if fields <> "" then
            fields = fields & ","
         end if
      
         fields = fields & "`" & keys(i) & "`"

         ' Add value.
         
         data = obj(keys(i))
        
         if values <> "" then
            values = values & ","
         end if
      
         if (TypeName(data) = "String") or _
            (TypeName(data) = "Date") then
            values = values & "'" & data & "'"
         else
            values = values & data
         end if
      end if
   next
   
   ' Insert the record.
   
   Entity_Insert = DB_Insert(strConn, obj("_Table"), fields, values)
end function

' Entity_Update() updates the given object in the database.
'
function Entity_Update(strConn, obj)
   dim assignments
   dim items
   dim keys
   dim data
   dim where
   dim i
   
   assignments = ""
   keys = obj.Keys()
   items = obj.Items()

   for i = 0 to UBound(keys)
      if (Left(keys(i), 1) <> "_") and _
         (keys(i) <> obj("_PrimaryKey")) then

         ' Add assignment.

         data = items(i)
         
         if assignments <> "" then
            assignments = assignments & ","
         end if
      
         assignments = assignments & "`" & keys(i) & "` = "
         
         if (TypeName(data) = "String") or _
            (TypeName(data) = "Date") then
            assignments = assignments & "'" & data & "'"
         else
            assignments = assignments & data
         end if
      end if
   next

   ' Build where clause.
   
   where = obj("_PrimaryKey") & " = "
   data = obj(obj("_PrimaryKey"))
   
   if (TypeName(data) = "String") or _
      (TypeName(data) = "Date") then
      where = where & "'" & data & "'"
   else
      where = where & data
   end if

   ' Update database.
   
   Entity_Update = DB_Update(strConn, obj("_Table"), assignments, where)
end function

' Entity_Delete() deletes the given object from the database.
'
function Entity_Delete(strConn, obj)
   dim data
   dim where

   ' Build where clause.
   
   where = obj("_PrimaryKey") & " = "
   data = obj(obj("_PrimaryKey"))
   
   if (TypeName(data) = "String") or _
      (TypeName(data) = "Date") then
      where = where & "'" & data & "'"
   else
      where = where & data
   end if

   ' Delete record.
   
   Entity_Delete = DB_Delete(strConn, obj("_Table"), where)
end function

' Entity_Clone() clones the given object.
'
function Entity_Clone(obj)
   dim newObj
   dim keys
   dim i

   ' Create an empty object.

   set newObj = Server.CreateObject("Scripting.Dictionary")
   
   keys = obj.Keys()
   
   for i = 0 to UBound(keys)
      newObj.Add keys(i), obj(keys(i))
   next

   set Entity_Clone = newObj
end function

' Entity_URLEncode() encodes the given Dictionary object into query 
' string format (e.g. a=1&b=2) using the given name as a tag for the object
' fields.
'
function Entity_URLEncode(name, obj)
   dim data
   dim keys
   dim i

   ' Get the keys (field names) of the object.

   data = ""
   keys = obj.Keys()

   ' Loop through the keys. For each, add the key name and the key value to 
   ' the query string data. The given object name is prepended to the key 
   ' name, so that it can be decoded later and so that multiple objects can 
   ' be encoded without field name collisions. (Basically, this allows each 
   ' object to  have its own "name space" in the query string.)
   '
   ' Here is an example:  
   '
   ' name = "article"
   ' key =  "title"
   ' article("title") = "foo"
   '
   ' => data = "article_title=foo"

   for i = 0 to UBound(keys)
      data = data & _
         Server.URLEncode(name & "_" & keys(i)) & "=" & _
         Server.URLEncode(CStr(obj(keys(i))))

      ' If there is more than one keys, append "&", which is the field
      ' separator in a query string.
      
      if i < UBound(keys) then
         data = data & "&"
      end if
   next

   ' Return the query string data.

   Entity_URLEncode = data
end function

' Entity_URLDecode() decodes a object from a query string. When it is
' done the given object contains the decoded data. The fields defined in the
' given object are extracted from the query string of the given request 
' object and stored in the given object. The given object name is used as
' a tag for the object fields and must the name (case-sensitive) that was
' used to encode the object originally.
'
sub Entity_URLDecode(req, objectName, obj)
   dim keys
   dim fieldName
   dim fieldData
   dim fieldValue
   dim i

   ' Get the keys (field names) from the object.

   keys = obj.Keys()

   ' Loop through the fields. For each, decode the field and its data from
   ' the given request object and store the data in the given object.

   for i = 0 to UBound(keys)
      ' Get the field name.

      fieldName = keys(i)

      ' Get the field data from the request object.

      fieldData = req(objectName & "_" & fieldName)

      ' Convert the field data from string to the type of the object field.
      
      fieldValue = Entity_ConvertType(fieldData, TypeName(obj(fieldName)))

      ' If the type conversion did not work (null was returned), then just
      ' store the data as-is.
      
      if IsNull(fieldValue) then
         fieldValue = fieldData
      end if

      ' Store the field in the given object.

      obj(fieldName) = fieldValue
   next
end sub

' Entity_WriteInternalAttributes() writes all attributes that start with "_" as
' hidden form fields.
'
sub Entity_WriteInternalAttributes(obj, prefix)
   dim keys
   dim i
   
   keys = obj.Keys()
   
   for i = 0 to UBound(keys)
      if Left(keys(i), 1) = "_" then
         Response.Write _
            "" & vbCrLf
      end if
   next 
end sub

' Entity_ConvertType() converts the given value to the given type.
'
function Entity_ConvertType(value, toType)
   dim result
   
   select case toType
      case "String"
         result = CStr(value)

      case "Date"
         result = CDate(value)

      case "Integer"
         result = CInt(value)

      case "Long"
         result = CLng(value)

      case "Double"
         result = CDbl(value)
   end select

   Entity_ConvertType = result
end function
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