how to create a new array of strings

Question

I don't understand the way this is working. Im tring to create an array of strings from a list of strings. I count the number of strings in the list and then want to create an array of these strings. I was doing some testing and came up with this code:

string *newOrder;

int numNodes;

numNodes = alphaTree.numNodes();

newOrder = new string [numNodes];

newOrder[0] = "This is";
newOrder[1] = "a test";
newOrder[2] = "To see";
newOrder[3] = "If this";
newOrder[4] = "will work";

The results are that newOrder acts like it is a single string array having the vaule "This is". What am I doing wrong?

Please use std::vector. All use of new, new[], delete, delete[], ~T(), malloc, or free should be avoided except in a class that does nothing else but call them (for example, when writing a custom smart pointer or typesafe union). — o11c
– o11c, Commented Sep 28, 2014 at 4:07
Too new to programing. I don't know what a smart pointer or typesafe union is, but I'd like to know your reasoning for not using the code you listed above. — user3600424
– user3600424, Commented Sep 29, 2014 at 4:59
The point is only advanced things such as smart pointers and typesafe unions should call those things directly. Using a vector prevents leak of memory and can protect against buffer overruns. — Neil Kirk
– Neil Kirk, Commented Oct 1, 2014 at 23:02
Voting to close as the code is correct but the problem was misunderstanding of the debugger view. — M.M
– M.M, Commented Oct 2, 2014 at 1:05

Dr. Debasish Jana · Accepted Answer · 2014-09-28 02:27:17Z

1

Check if numNodes = alphaTree.numNodes(); is returning desired size.

The following is a correct piece of code, allocates for 5 strings, and assigns.

newOrder = new string [5];
newOrder[0] = "This is";
newOrder[1] = "a test";
newOrder[2] = "To see";
newOrder[3] = "If this";
newOrder[4] = "will work";

If you execute the following statement:

cout << newOrder[2] << endl;

This will print: To see

answered Sep 28, 2014 at 2:27

Dr. Debasish Jana

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6 Comments

user3600424 Over a year ago

it returns 5. Using the debugger in VS I can see the end result after all the strings have been assigned and all it shows is "This is". It has index numbers next to each letter when I expand it in the locals window.

user3600424 Over a year ago

Ahh yes. I guess since newOrder is a pointer it will only show the first element in the array that is pointing to. Thanks! Alow my self... to confuse...my self....

PaulMcKenzie Over a year ago

@user3600424 If the problem is the debugger, then reword your question that it is a debugger display issue, not a programming issue. Right now, your question sounds like a programming issue.

user3600424 Over a year ago

Perhaps my comments were worded poorly. This was a programming issue.

PaulMcKenzie Over a year ago

@user3600424 So how is the answer you accepted different than the code you posted in your question? I see no difference, except that we don't see a couple of variable declarations, and that numNodes is used instead of 5.

|

o11c · Accepted Answer · 2014-10-01 22:56:47Z

0

using std::string;
using std::vector;

// from an initializer_list
vector<string> newOrder1 = {
    "This is",
    "a test",
    "To see",
    "If this",
    "will work",
};

// as a sequence of appends
// often used in a loop if an iterator is not applicable
vector<string> newOrder2;
newOrder2.push_back("This is");
newOrder2.push_back("a test");
newOrder2.push_back("To see");
newOrder2.push_back("If this");
newOrder2.push_back("will work");

// from an iterator-pair over any standards-compliant container
vector<string> newOrder3(alphaTree.begin(), alphaTree.end());

answered Oct 1, 2014 at 22:56

o11c

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