How to convert a vector to a vector/string

Question

We have a legacy method that returns a vector of char pointers i.e., vector<char *>. Now, I need to process only strings (std::string). How can I do this?

This question may sound simple, but I run into couple of websites which depicted that these sort of considerations might lead to memory leaks.

Now, I either want to get a vector<string> or even a string without any memory leaks. How can I do this?

There's nothing inherently leaky about using vectors, except that they're relatively more memory-expensive while alive. Just use the regular vector operations and destruct it when you're done. char* can easily be converted to a proper c++ string using the string library. — Rag, Aug 01 '11 at 15:36

score 22 · Answer 1 · answered Aug 01 '11 at 15:35

22

The conversion is quite straightforward:

std::vector<char*> ugly_vector = get_ugly_vector();
std::vector<std::string> nice_vector(ugly_vector.begin(), ugly_vector.end());

Once you've done that, though, you still need to make sure that the objects pointed to by the pointers in ugly_vector are correctly destroyed. How you do that depends on the legacy code you are utilizing.

answered Aug 01 '11 at 15:35

James McNellis

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Is the vector constructor calling the string constructor behind the operation? – zw324 Aug 01 '11 at 15:38
You beat me to it. That's a trick I like for converting argv[] – Martin York Aug 01 '11 at 15:47
4

`std::vector args(argv, argv + argc); // very handy` – James McNellis Aug 01 '11 at 15:51

score 2 · Answer 2 · edited Aug 01 '11 at 15:51

2

Use std::copy:

using namespace std;
vector<char*> v_input;
...
// fill v_input
...
vector<string> v_output;

v_output.resize(v_input.size());
copy(v_input.begin(), v_input.end(), v_output.begin());

edited Aug 01 '11 at 15:51

James McNellis

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answered Aug 01 '11 at 15:36

Constantinius

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score -1 · Accepted Answer · answered Aug 01 '11 at 15:36

-1

well, depending on the performance requirements, you could just construct a std::string as needed. Like this:

for(std::vector<char*>::const_iterator it = v.begin(); it != v.end(); ++it) {
    std::string s = *it;

    // do something with s
}

answered Aug 01 '11 at 15:36

Evan Teran

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How to convert a vector to a vector/string

3 Answers3

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