mybooks | 白乔编著《把脉VC》《标准C开发入门与编程实践》的源代码

Ok, I understood your problem. For every bookID, you fetch its data from Google Books, and now you want to not hit the api for already loaded items.

Simply, create a global variable for ArrayList as

The destructuring of ({navigation}) vs. (props) does not make a difference. The important thing is what props are provided when the component is called.

Writing ({navigation}) means that your component expects to be called with a navigation prop. It doesn't provide that prop.

The top-level screens such as MyBooks and BooksMenu will be called with the props navigation and route when they are rendered by the Navigator. BooksCell is not a screen so React Navigation will not provide it with any props.

If you want to use the prop navigation in BooksCell then you must provide it. You can pass it down from a parent which has the prop.

I would suggest a different approach. This may not directly answer your question as to why Tracker.autorun is not working as you expected, but I think will help you more than if looking for an answer to your original question.

I believe the recommended pattern for using reactive data sources in meteor with react is to use useTracker. Here is your code rewritten in that pattern:

Use executeUpdate for database write operations

I offer to you 3 methods to accomplish your end goal - admittedly only one uses simple_xml

Method #1: Simple XML As you wish to display ALL websites per row in the table you need nested queries. The outer query to return the rows ( bookshelfs ) and the inner query to return the books on that bookshelf. When it comes to the stock node that does not exist for particular books I used a ternary operator to select another value if the stock tag did not exist.

The issue is that the category variable will be each key, which is a string. You should change the category.map to myBooks[category].map()

This is not how you store values...

In the table Accounts there is a column my_booksID referencing my_booksID of MyBooks. Why?
Do you plan to have a new row in Accounts for the same user every time they take a book?

Instead, you should have a column user_id in MyBooks referencing user_id in Accounts.
This way you make MyBooks the linking table between Accounts and MyBooks.

When a user takes a book out from the library, you will add a new row in MyBooks with the user_id of the user and the bookID of the book.

Also, in SQLite there are no VARCHAR and TIMESTAMP data types (check Datatypes In SQLite Version 3).
In the case of VARCHAR use TEXT and for TIMESTAMP, if you want to store dates in the format YYYY-MM-DD (which is the only valid date format for SQLite) use TEXT, or if you want to store dates as unix timestamps use INTEGER.

By default a DetailView will look for a url parameter named pk or slug to obtain the item. But here you named the parameter book_id.

You can however specify in the pk_url_kwarg [Django-doc] the name of the url parameter: