Скачать или смотреть How to Properly Use push_back with Vectors in C+ + : Avoiding Common Pitfalls

Discover how to use `std::vector` with `push_back` in C+ + , avoiding common mistakes that lead to unexpected results. Get simple solutions and best practices to manage character arrays effectively.
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How to Properly Use push_back with Vectors in C+ + : Avoiding Common Pitfalls

When working with dynamic arrays in C+ + , specifically with std::vector, it's essential to understand how memory management works. A common mistake can lead to confusing behaviors when adding items to a vector using the push_back method. In this guide, we'll unpack a specific example where the user experiences unexpected results while trying to add character arrays to a vector.

The Problem: Unexpected Duplicates in Vector

Suppose you have an array of character pointers and you're attempting to add items to a vector like this:

[[See Video to Reveal this Text or Code Snippet]]

Upon looping through Lista to print its contents, you encounter the following output, which shows unexpected identical values:

[[See Video to Reveal this Text or Code Snippet]]

The Confusion

Here, all the entries in your vector point to the same memory location—the array txt. Each time you modify txt, you overwrite its content, causing all pointers in Lista to end up with the same value: the last modified content (num5).

The Solution: Storing Unique Strings

To store different strings in each element of Lista, you have a few options:

1. Using std::string

The easiest and most efficient solution is to use std::string instead of char*. This approach automates memory management:

[[See Video to Reveal this Text or Code Snippet]]

By using std::string, each entry in Lista manages its memory and ensures that the contents remain unique.

Accessing char* from std::string

If you need to obtain a pointer to the underlying character array from std::string, you can do so using:

[[See Video to Reveal this Text or Code Snippet]]

2. Manual Memory Allocation

If you prefer sticking to char*, you'll need to allocate memory for each string separately to ensure they don't overlap:

[[See Video to Reveal this Text or Code Snippet]]

Important Note: This method requires careful memory management; failure to release allocated memory leads to leaks.

Conclusion

In summary, when using std::vector with character arrays, it’s crucial to understand memory allocation. Using std::string is generally the best practice, simplifying storage and management of strings. However, if you need to work with raw character pointers, ensure that each pointer points to a uniquely allocated memory space.

Avoiding these pitfalls will help you create cleaner, more predictable C+ + code.