What is the issue if we use text1 =text2? What is the right method to copy text between two text variables? - ewam

Question

I am getting error in compile mode for the statement text1=text2. What is the issue with the statement and how can we resolve it?

Answer 1

There is a section in the Wynsure Development Rules dedicated to this question, look for the section "14.3 Texts" I'll summarize:
A text variable is a pointer to a buffer that gets automatically reallocated as we write to the text, therefore the memory location differs as the text grows, changes or shrinks. For this reason the pointer isn't contant. eWAM automatically allocates a new larger buffer and copies the content of the old buffer to the new buffer, frees the old buffer and then updates the MyText pointer to point to the new buffer.
Shallow Assignment
It is the most dangerous operation if you really do not understand how text variables work.
For example the following code will crash (as a general rule what will cause a crash is either accessing to a memory location that has been freed or freeing the same memory location twice.)
MyText2 = MyText1
Write(MyText1, ….)
Blank(MyText1)
Blank(MyText2) // Crash
The shallow assignment MyText2 = MyText1 simply copy pointers. It does not duplicate buffers.
When copying a text from one variable to another one, use a deep copy :=
If you use = it points to the original text var address. And then when you set the second text to blank, it in fact sets the original text to blank (dispose).
Dedicated Text Methods
Text has a number of custom methods that handle them correctly such as the var.type.write function
var.type.blank function
Procedure Test
var tmpText : Text
tmpText.type.Write(‘Hello’, #tmpText)
tmpText.type.blank(#tmpText)
endProc
Note that we always need to blank the old variable text after we move the content so that there isn't a memory leak.
procedure AnotherProcedure
Var MyText : Text
Var tmpText : text
tmpText= GetXXXText
Write(MyText, tmpText )
tmpText.type.blank(#tmpText)
endproc