c++: new multi dimensional array of strings [duplicate]

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Possible Duplicate:

C++ multi dimensional array

I'm trying to create a class that creates an arbitrary sized array of strings based on one of the objects constructor arguments.

Here, the code for the object constructor I'm trying so far:

commandSpec::commandSpec(int numberOfCommands)
{
    std::string * commands = new std::string[3][numberOfCommands];
}

I get an error: 'numberOfCommands cannot appear in a constant expression', could someone show me the correct way to specify an array in an object that i d开发者_运维问答ont know the size of until execution.

Thanks, j

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This should probably be implemented as a structure and a vector, like this:

struct command {
    std::string first;
    std::string second;
    std::string third;
};

commandSpec::commandSpec(int numberOfCommands)
{
    std::vector<command> commands(numberOfCommands);
}

Of course, you should choose appropriate names for the members of command.

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Variable length arrays are allowed only when allocating on heap.

You need to allocate the array in 2 steps - first allocate array with length 3 (from pointers) and then loop through the 3 elements and allocate new string for each.

I'd recommend you to use std::vector instead.

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I would use a std::vector instead, makes life easier:

commandSpec::commandSpec(int numberOfCommands)
{
    std::vector<std::vector<std::string>> mystrings(numberOfCommands);
}

---

Invert the order of the dimensions...

commandSpec::commandSpec(int numberOfCommands)
{
    std::string (*commands)[3] = new std::string[numberOfCommands][3];
}

However, I highly recommend you consider using vectors instead.