C++ Appending to an array

Question

const int fileLength = fileContent.length();
    char test[1000];
    for (int p = 0; p < fileLength; ++p){
        test[p].append(fileContent[p]); // Error: expression must have class type
    };

I'm attempting to append the characters of a text file into an array which i've created. Though I'm getting the error " expression must have class type ". Tried googling this error to no avail.

Possible duplicate of [The Definitive C++ Book Guide and List](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) — BoBTFish, Dec 22 '15 at 13:44
If you want to use 'append', why do you use a char array instead of a string or vector? — DrDonut, Dec 22 '15 at 13:47

Martin Bonner supports Monica · Answer 1 · 2015-12-22T13:51:33.287

5

test is an array of char. test[p] is a char. char does not have any members. In particular, it does not have an append member.

You probably want to make test a std::vector<char>

    const auto fileLength = fileContent.length();
    std::vector<char> test;
    for (const auto ch : fileContent)
    {
        test.push_back(ch);
    }

or even:

    std::vector<char> test( fileContent.begin(), fileContent.end() );

if you then really need to treat the test as an array (because you are interfacing to some C function for example), then use:

    char* test_pointer = &*test.begin();

If you want to use it as a nul-terminated string, then you should probably use std::string instead, and get the pointer with test.c_str().

edited Dec 22 '15 at 13:51

answered Dec 22 '15 at 13:47

Martin Bonner supports Monica

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@LogicStuff: Was that addressed at me, or the OP? I say "probably" in a couple of places, because there are occasions where that advice doesn't apply. – Martin Bonner supports Monica Dec 22 '15 at 13:56
OP Deleted his comment, so did I just now. – LogicStuff Dec 22 '15 at 13:56

score 0 · Answer 2 · answered Dec 22 '15 at 14:11

char array does not have any member function by the name append .However , std::string does have one member function named append like below :

string& append (const char* s, size_t n);

I think you by mistake have used char array instead of std::string . std::string will resolve this problem like below :

const int fileLength = fileContent.length();
    string test;
    for (int p = 0; p < fileLength; ++p){
        test.append(fileContent[p],1); // Error: expression must have class type
    };

Better way would be string test(fileContent) .You can access test just like a array .Refer string class for more details .

C++ Appending to an array

2 Answers2