Hi,

I'm following the example on

https://dlang.org/phobos/std_csv.html

    class Layout
    {
        int value;
        double other;
        string name;
        int extra_field;  // un-comment to see the error
    }

void main()
{
    import std.csv;
    import std.stdio: write, writeln, writef, writefln;
    import std.algorithm.comparison : equal;
    string text = "a,b,c\nHello,65,2.5\nWorld,123,7.5";

    auto records =
        text.csvReader!Layout(["b","c","a"]);  // Read only these column
    foreach (r; records) writeln(r.name);
}

This works fine so far, but if I un-comment the extra_field line, I got runtime error:

core.exception.ArrayIndexError@/dlang/dmd/linux/bin64/../../src/phobos/std/csv.d(1209): index [3] is out of bounds for array of length 3
----------------
??:? _d_arraybounds_indexp [0x5565b4b974d1]
/dlang/dmd/linux/bin64/../../src/phobos/std/csv.d:1209 pure @safe void std.csv.CsvReader!(onlineapp.Layout, 1, immutable(char)[], dchar, immutable(char)[][]).CsvReader.prime() [0x5565b4b73ed2]
/dlang/dmd/linux/bin64/../../src/phobos/std/csv.d:1154 pure @safe void std.csv.CsvReader!(onlineapp.Layout, 1, immutable(char)[], dchar, immutable(char)[][]).CsvReader.popFront() [0x5565b4b73c80]
/dlang/dmd/linux/bin64/../../src/phobos/std/csv.d:1069 pure ref @safe std.csv.CsvReader!(onlineapp.Layout, 1, immutable(char)[], dchar, immutable(char)[][]).CsvReader std.csv.CsvReader!(onlineapp.Layout, 1, immutable(char)[], dchar, immutable(char)[][]).CsvReader.__ctor(immutable(char)[], immutable(char)[][], dchar, dchar, bool) [0x5565b4b73ae8]
/dlang/dmd/linux/bin64/../../src/phobos/std/csv.d:366 pure @safe std.csv.CsvReader!(onlineapp.Layout, 1, immutable(char)[], dchar, immutable(char)[][]).CsvReader std.csv.csvReader!(onlineapp.Layout, 1, immutable(char)[], immutable(char)[][], char).csvReader(immutable(char)[], immutable(char)[][], char, char, bool) [0x5565b4b735f3]
./onlineapp.d:18 _Dmain [0x5565b4b72ca4]

I'm just wondering how to work-around this?

Thanks.

        text.csvReader!Layout(["b","c","a"]);  // Read only these column

The intention is very clear: only read the selected columns from the csv, and for any other fields of class Layout, just ignore (with the default D .init value).

On Sunday, 2 October 2022 at 19:48:52 UTC, mw wrote:

        text.csvReader!Layout(["b","c","a"]);  // Read only these column

Why don't you do this? For example you can try the following?

```d
import std.csv, std.math.algebraic : abs;

     string str = "a,b,c\nHello,65,63.63\n➊➋➂❹,123,3673.562";
     struct Layout
     {
         int value;
         double other;
         string name;
     }

     auto records = csvReader!Layout(str, ["b","c","a"]);

     Layout[2] ans;
     ans[0].name = "Hello";
     ans[0].value = 65;
     ans[0].other = 63.63;
     ans[1].name = "➊➋➂❹";
     ans[1].value = 123;
     ans[1].other = 3673.562;

     int count;
     foreach (record; records)
     {
         assert(ans[count].name == record.name);
         assert(ans[count].value == record.value);
         assert(abs(ans[count].other - record.other) < 0.00001);
         count++;
     }
     assert(count == ans.length);
```

SDB@79

On Monday, 3 October 2022 at 18:02:51 UTC, Salih Dincer wrote:

        text.csvReader!Layout(["b","c","a"]);  // Read only these column

```d
import std.csv, std.math.algebraic : abs;

     string str = "a,b,c\nHello,65,63.63\n➊➋➂❹,123,3673.562";
     struct Layout
     {
         int value;
         double other;
         string name;
     }

You didn't get my question, please add:

int extra_field;  // un-comment to see the error

to the struct, then you will see the error.