Android Question Best coding

Discussion in 'Android Questions' started by yfleury, Aug 17, 2019.

  1. yfleury

    yfleury Active Member Licensed User

    Hi all!

    What is the best code between to code bellow to insert data in DB
    I have to dim many variables. I want to know if it's better to dim variables outside the for next loop and affecting variable inside for next like this
    dim name1 as string
    dim name2 as int
    dim name3 as double
    dim sqlRequest as string
    for x=0 to field.size-1
    "insert into .... blabla
    Or redim inside the for next like this

    for x=0 to field.size-1
    dim name1 as string="blalba"
    dim name2 as int=112345
    dim name3 as double=1.12345
    dim sqlRequest as string
    "insert into .... blabla
    I just want to have the best coding practice

    Note: the code is only to illustrade my idea.
    wynds likes this.
  2. DonManfred

    DonManfred Expert Licensed User

    redim and initialize '(if needed) inside the loop.
    Last edited: Aug 17, 2019
    fixit30 and yfleury like this.
  3. rraswisak

    rraswisak Member Licensed User

    in my opinion, if you just want to reuse (temporary) variable to hold value for query statement then i would recommend to declare out-side of looping, make sure using begintransaction and commit before and after looping
  4. fixit30

    fixit30 Active Member Licensed User

    yfleury likes this.
  5. yfleury

    yfleury Active Member Licensed User

    Thanks all It's appreciate for tip... So I am on good way without rewrite my code.
  6. agraham

    agraham Expert Licensed User

    B4X only has two scopes for variables, global and local. It doesn't matter where in the Sub a variable is Dimmed, its actual declaration will be hoisted to the start of the Sub and it will be visible anywhere in the Sub.

    For primitive types if doesn't really matter if you Dim them within the loop or outside, although each Dim will reset the variable to its default value, such as 0 for an Int or an empty string for a String unless you also do an assignment to that variable.

    However for reference types there is a(n often not-so) subtle difference depending on the position of any Dim statement that can trip you up. Whenever you Dim a reference type the variable is assigned a new instance of that type so if you Dim it once outside the loop and use it inside the loop every pass round the loop will manipulate the same object. If you Dim it inside the loop a new instance is created for each pass round the loop. This is important if you want to save such instances each time round the loop when you must Dim inside the loop otherwise you will end up with only a single instance of that type, though perhaps saved in multiple places, that reflects the values given it in the last pass round the loop. Hint - if it needs Initialize called on it it is a reference type.
    Last edited: Aug 18, 2019
  7. mcqueccu

    mcqueccu Active Member Licensed User

    Depends on what you will be using your variable for, it can be Declared outside the loop or inside the loop.

    Outside the loop if you will perform some operation on the variable - example you are receiving some values from DB and you need to sum them to a variable

    Declaring inside the loop will reset variable everytime
    yfleury likes this.
  8. AnandGupta

    AnandGupta Active Member Licensed User

    Agraham explained Don's '(if needed)' :D


    yfleury likes this.
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