Question about Type and Each command
Blitz3D Forums/Blitz3D Beginners Area/Question about Type and Each command
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Please try this source:Type chair Field colour$ Field Height% End Type mychair1.chair = New chair mychair2.chair = New chair mychair1\colour$="brown" cont=1 For mychair1.chair= Each chair Print "ELEMENT: "+cont+" - "+mychair1\colour$ e$=Input() cont=cont+1 Next End Is it normal mychair1 has two elements ?? I'm using B+. Thanks. |
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| Yes it is normal, they are indeed two different pointers, but both point to the same structure; that means that they go through the same list, thus the same element collection. If you want two different lists, you can choose between: 1) make two different type structure and pointers (type chair_1 and chair_2, pointer mychar_1 and mychar_2) OR 2) use only one type structure and one pointer, and add an additional field - ex. ID - which can be set each time you create a new element. Example (one structure and one pointer): Type chair Field ID ;--------> New Field added ! Field colour$ Field Height% End Type mychair.chair = New chair mychair.ID = 1 ;here we set the new ID field mychair\colour$="Blue" mychair.chair = New chair mychair.ID = 2 ;here we set the new ID field mychair\colour$="brown" cont=1 ;Display only the chair with ID = 1 For mychair.chair= Each chair If mychair\ID = 1 then Print "ELEMENT: " + cont + " - "+mychair\colour$ e$=Input() cont=cont+1 EndIf Next End Personally, I would use the 2nd choice. Sergio. |
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| 'mychair1' is just a pointer variable that points to an element, it doesn't actually contain elements. The For Each loop is iterating through the chain of elements that you've created of type 'chair', and the pointer to each element is being placed in 'mychair1.chair' during each pass through the loop, overwriting the previous pointer value in 'mychair1.chair'. |
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| Thanks for reply. So mychair1 and mychair2 are pointers to newly created elements of ONE list. Then, the TYPE command DOES create a list and the NEW command adds elements to that list. I thought the TYPE command was more like STRUCT in C and that a list was created by NEW command. ;IT CREATES A LIST CALLED chair Type chair Field colour$ Field Height% End Type ;IT ADDS TWO ELEMENTS TO LIST chair AND ASSIGNS POINTERS ;TO VARIABLES mychair1 AND mychair2 . mychair1.chair = New chair mychair2.chair = New chair mychair1\colour$="brown" cont=1 For mychair1.chair= Each chair Print "ELEMENT: "+cont+" - "+mychair1\colour$ e$=Input() cont=cont+1 Next End It's a bit different from C or other Basic dialects. It can be a bit confusing if one knows how lists work in C. In PureBasic for example, it would be:
;IT DEFINES A NEW TYPE
Structure chair
colour$
height.l
EndStructure
OpenConsole()
;IT CREATES TWO LISTS OF chair TYPE
NewList mychair1.chair()
NewList mychair2.chair()
;IT ADDS ONE ELEMENT TO LIST mychair1
AddElement(mychair1())
;IF I NEED A POINTER TO THAT ELEMENT:
;*p=AddElement(mychair1())
mychair1()\colour$="brown"
cont=1
ResetList(mychair1())
While NextElement(mychair1())
PrintN("ELEMENT: "+Str(cont)+" - "+mychair1()\colour$)
e$=Input()
cont=cont+1
Wend
End
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| Yep, you've got it. I agree with you that the way types work right now, could be confusing. Perhaps this will change in the future... Sergio. |
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