Delphi - Re-split an array of string? - arrays

Question

Let's say I have a string like this :
string1 := 'me,email1,you,email2,him,email3,them,email4';
To turn this into an array of string I simply do :
array1 := SplitString(string1,',');
This works fine.
But then, I get an array like :
array1[0] -> me
array1[1] -> email1
array1[2] -> you
array1[3] -> email2
array1[4] -> him
array1[5] -> email3
array1[6] -> them
array1[7] -> email4
I've searched a long time how to insert into SQLIte with this but there is no using
for i:= 0 to length(array1) -1
SQLExecute('INSERT INTO table(name,email) VALUES("'+array1[i]+'","'+array1[i+1]+'"');
because index 0 will be inserted as name with index 1 as email, but on the next turn, index 1 will be inserted as name with index 2 as email, when index 1 is en email, and index 2 a name... do you see the problem ?
I thought about re-spliting the first array into a second one by changing the initial string format into :
string1 := 'me-email1,you-email2,him-email3,them-email4';
to split a first time on the ' and a second time on the -, to get a 2 dimensional array, but seems this concept is over my knowledge at the moment :)
Just for the record, the Delphi RAD I'm using is quite recent, and only a few functions / tools are available at the moment.
How would you insert into sql ? Would you keep the original String format, or change it to get a 2 dimensional array ?

Answer 1

Iterate in pairs:
for i := 0 to length(array1) div 2 - 1 do
SQLExecute('INSERT INTO table(name,email) VALUES("'+array1[i*2]+'","'+array1[i*2+1]+'"');

Answer 2

You just should not use per-INSERT FOR-loop here.
It is not suited for it and it is dangerous if your string would have 3 or 7 or any other odd number of elements.
Also splicing random data right into the SQL command is extremely unreliable and fragile. http://bobby-tables.com/
You should either use a WHILE-loop with a sliding fetcher or tick-tock (finite state machine) swinging in one-per-string FOR-loop.
var q: TQuery;
// some Query-component of any library,
// including DBX, AnyDAC/ FireDAC mORMot or any other library you would use
var sa_OK, sa_err1, sa_err2: TArray<string>;
// common preparations for both methods
q.ParamCheck := True;
q.SQL.Text := 'INSERT INTO table(name,email) VALUES( :PName, :PMail )';
q.Prepared := True;
sa_OK := TArray<string>.Create( 'me','email1','you','email2','him','email3','them','email4');
// eeeaaasy example
sa_err1 := TArray<string>.Create( 'me','email1','you','email2','him');
// check this out-of-sync error too - it can happen! you should be pre-aware!
sa_err2 := TArray<string>.Create( 'Sarah O''Connor','email1','"Bobby F. Kennedy"','email2','him'#0'again','email3');
// not the letters you expected - but they can come too
Procedure Method1_Fetcher( const sa: array of string );
var i: integer;
s: string;
function Fetched: Boolean;
begin
Result := i <= High(sa);
if Result then begin
s := sa[i];
Inc(i);
end;
end;
Begin
i := Low(sa);
while true do begin
if not Fetched then break;
q.Params[1].AsWideString := s;
if not Fetched then break;
q.Params[2].AsWideString := s;
// ...you can easily add more parameters for more columns
// if not Fetched then break;
// q.Params[3].Value := s;
// ... or you can make a loop
// FOR j := 0 to q.Params.Count - 1 DO ... q.Params[j] :=...
// only executing insert if ALL the columns were filled
q.ExecSQL;
end;
q.Transaction.CommitWork;
End;
Procedure Method2_TickTock( const sa: array of string );
var i, FSM: integer;
Begin
FSM := 0;
for i := Low(sa) to High(sa) do begin
if FSM = 0 then begin
q.ParamByName('PName').AsWideString := sa[i];
FSM := 1; // next mode of tick-tock
Continue;
end;
if FSM = 1 then begin
q.ParamByName('PMail').AsWideString := sa[i];
q.ExecSQL;
// only executing insert after the last column was filled
FSM := 0; // next mode of tick-tock
Continue;
end;
/// would only come here if we made some mistake above
/// and FSM got impossible value - so no "Continue" was executed
/// show error and exit
raise EInvalidOperation.CreateFmt('FSM = %d', [FSM]);
end;
q.Transaction.CommitWork;
End;
Procedure Method3_SimplifiedFSM( const sa: array of string );
// this method is actually are streamlined method #2
// it can be made because all our steps are TOTALLY identical
// ( sans optional insert execution )
var i, FSM: integer;
Begin
FSM := 0;
for i := Low(sa) to High(sa) do begin
q.Params[ FSM ].AsWideString := sa[i];
Inc( FSM );
if FSM >= q.Params.Count then begin
q.ExecSQL; // only after (if ) last of all columns filled!
FSM := 0;
end;
end;
q.Transaction.CommitWork;
End;
Now you can debug calls like Method1(sa_OK) or Method2(sa_err1) and see how it is working and how it deals with errors