3.4.4 Arrays and Tables

If the table does not have a tocom tag method (for Lua 4) or __tocom metamethod (for Lua 5), LuaCOM first checks if the table can be describing a variant. A table is a variant if it has a Type field. This field must have a string that tells how the Value field of the table must be converted. Possible values for Type are string, bool, error, null, currency, decimal, double, float, int8, uint8, int4, uint4, int2, uint2, int1, verb+uint1+, int, and uint. Each corresponds to a variant type. If the table is not describing a variant, then it may be describing a date. A table is a date if it has one of those fields: Day, DayOfWeek, Month, Year, Hour, Minute, Second, Milliseconds. LuaCOM initializes the date with the fields that are present; the others are kept at their default values. If the table is not a date, LuaCOM converts Lua tables to SAFEARRAY's and vice-versa. To be converted, Lua tables must be ``array-like'', that is, all of its elements must be or ``scalars'' or tables of the same length. These tables must also be ``array-like''. Here are some samples of how is this conversion done:

Lua table	Safe Array
table = {"name", "phone"}	$$\left[\begin{array}{cc} ''name'' & ''phone'' \\ \end{array}\right]$$
table = {{1,2},{4,9}}	$$\left[\begin{array}{cc} 1 & 2 \\ 4 & 9 \\ \end{array} \right]$$

If the table has the conversion tag/metamethod, LuaCOM uses it to guide the conversion. If the tag/metamethod is a method, LuaCOM calls it, passing the table and the COM type. The method should return a COM object that LuaCOM will pass on. If the tag/metamethod is a table, LuaCOM will look for a typelib field, an interfacefield , and a coclass field, and pass those as arguments to the ImplInterfaceFromTypelib API call. If the table does not have a typelib field, LuaCOM will look for a progid field and an interface field, and pass those to the ImplInterface API call. Either way, LuaCOM will pass the returned object to COM.