如何从 C++ 中的结构数组打印所有内容？
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How to print everything from an struct array in c++?
提问by paddy
I have a structured a data type called bookStruct and books is the name of the variable associated with the bookStruct data type. book[10] is the array that is 10 characters long and has 4 characters of data, meaning book[0] to book [3] have datas in them when the rest are empty (o values). Now I want to print the datas that are availabe already in the array and not print the ones that are empty otherwise 0. I tried the below code, with no luck.What am I doing wrong here?
我有一个名为 bookStruct 的结构化数据类型，books 是与 bookStruct 数据类型关联的变量的名称。book[10] 是长度为 10 个字符的数组，有 4 个字符的数据，这意味着 book[0] 到 book [3] 在其余为空时（o 值）中有数据。现在我想打印数组中已经可用的数据，而不打印那些为空的数据，否则为 0。我尝试了下面的代码，但没有运气。我在这里做错了什么？
for (int i=0;i<MAX_BOOKS && books[i]!='struct bookStruct
{
string bookTitle;
int bookPageN;
int bookReview;
float bookPrice;
};
bookStruct books[10];
';i++)
{
cout << "Book Title: " << books[i].bookTitle << endl;
cout << "Total Pages: " << books[i].bookPageN << endl;
cout << "Book Review: " << books[i].bookReview << endl;
cout << "Book Price: " << books[i].bookPrice<< "\n\n" << endl;
}
here is the declaration for book struct
这是 book struct 的声明
struct Book {
string title;
int pageN;
int review;
float price;
};
ostream& operator<<(ostream& os, const Book& book) {
return os << "Title: " << book.title << endl
<< "Pages: " << book.pageN << endl
<< "Review: " << book.review << endl
<< "Price:" << book.price << endl;
}
回答by Peter Wood
Overload the output operator. E.g:
重载输出运算符。例如：
Book book;
ostringstream oss;
oss << book;
Then you can output to any stream:
然后你可以输出到任何流：
bool bookHasTitle(const Book& book) {
return book.title.empty() == false;
}
Book books[10];
copy_if(books, books+10, ostream_iterator<Book>(cout, "\n"),
bookHasTitle);
To loop over all your books, copying to std::cout, only when a book has a title, you need std::copy_if:
要循环遍历所有书籍，复制到std::cout，仅当书籍具有标题时，您需要std::copy_if：
int numBooks = 0;
回答by paddy
It's a little hard to tell what's being asked here. You see, it's quite easy to just keep count of how many books you have stored:
很难说出这里问的是什么。你看，计算你存储了多少本书是很容易的：
for( int i=0; i<numBooks; i++ ) ...
When you add a book, you increment numBooksup until MAX_BOOKS.
当您添加一本书时，您会递增numBooks直到MAX_BOOKS。
for( int i=0; i<MAX_BOOKS && !books[i].bookTitle.empty(); i++ ) ...
If you don't want to do that, you certainly can't test books[i] != '\0'because that is testing the struct against a single character.
如果你不想这样做，你当然不能测试，books[i] != '\0'因为这是针对单个字符测试结构。
Instead, you might want to test books[i].bookTitle.size() != 0
相反，您可能想要测试 books[i].bookTitle.size() != 0
(or indeed !books[i].bookTitle.empty()).
（或确实!books[i].bookTitle.empty()）。
vector<bookStruct> books;
...
for( int i = 0; i < books.size(); i++ ) ...
Another alternative is to store books in a vectorinstead of an array, so you don't have to worry about maximum counts and current counts. The vector can shrink and grow for you.
另一种选择是将书籍存储在一个vector而不是数组中，因此您不必担心最大计数和当前计数。矢量可以为您缩小和增长。
