Tutorial

Using mdTypes [EN]

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While working with collections you may have to serialize its content. All collections can be casted to a normal String. You can use Cast, Str or the toString() method. While creating String representations is really easy, deserializing these Strings back to lists and maps may be harder. For this purpose we have a helper class:
- md/helper/mdCollectionsHelper

mdCollectionsHelper contains only a few static methods:

createList(String) As mdList(String)

createMap(String) As mdMap(String, String)

encode(String) As String

decode(String) As String

So, createList will generate a list out of the String, createMap a map. Because the representation of these Strings, it's important not to conflict with some special characters. To avoid problems, encode all Strings in you map containing these signs !"[]{}=,\r\n". On the other side you can use decode to get the correct value back.

Let's check out an example of how it might work:

'Include mdCollectionsHelper (it will include both mdList and mdMap for us)

#Include Once "md/helper/mdCollectionsHelper.bi"



'Prepare mdMap - mdCollectionsHelper will use this

mdMapDeclare(String, String)



'Sample class

Type MyClass

    Declare Constructor ()

    Declare Constructor (ByRef m As mdMap(String, String))



    Declare Operator Cast() As String



    As String label

    As Integer value

    As Double weight

End Type



Constructor MyClass()



End Constructor



'This constructor will get a map and fill the values of this class with the content of the map

Constructor MyClass(ByRef m As mdMap(String,  String))

    This.label = mdCollectionsHelper.decode(m.get("label")) 'if this data may be encoded, decode it again (see cast operator)

    This.value = ValInt(m.get("value"))

    This.weight = Val(m.get("weight"))

End Constructor



'The cast operator will create a map representation of the data in this class

Operator MyClass.Cast() As String

    Dim As String temp

    Dim As mdMap(String, String) m

    temp = m.put("label", mdCollectionsHelper.encode(This.label)) 'encoding is not necessary but not a bad idea for string data

    temp = m.put("value", Str(This.value))

    temp = m.put("weight", Str(This.weight))

    Return m

End Operator



Operator = (ByRef lhs As MyClass, ByRef rhs As MyClass) As Boolean

    Return Str(lhs) = Str(rhs)

End Operator



'Prepare sample data - I've filled it into an array and then into a list, but it's just an example

mdListDeclare(MyClass)



Dim As mdList(MyClass) listOfMyClass

Dim As MyClass firstArray(0 To 3)



For i As Integer = LBound(firstArray) To UBound(firstArray)

    firstArray(i).label = "label" & Str(i)

    firstArray(i).value = i

    firstArray(i).weight = i * 1.1



    listOfMyClass.add(firstArray(i))

Next



'Let's see the output for our created list - at this point we could send the data via internet or save it into a file or whatever...

Dim As String stringRepresentation = listOfMyClass

Print "List as string: " & stringRepresentation

Print



'Get a list back of the string and prepare a new array

Dim As mdList(String) listOfMaps = mdCollectionsHelper.createList(stringRepresentation)

Dim As MyClass newArray(0 To listOfMaps.size() - 1)



'Fill the array with the data of our string representation

For i As Integer = LBound(newArray) To UBound(newArray)

    newArray(i) = Type<MyClass>(mdCollectionsHelper.createMap(listOfMaps.get(i)))

    Print i, newArray(i)

Next



Sleep

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Zusätzliche Informationen und Funktionen

Das Tutorial wurde am 17.04.2014 von MOD angelegt.
Die aktuellste Version wurde am 31.07.2019 von MOD gespeichert.

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