CODEWITHSUNDEEP
javamath
nemke nemke
nemke nemke

Reputation: 191

How to manage adding and subtracting values based on user input?

I have a shopping cart that looks like this:

Title    Price    Amount    Total
Item1    20         3        60
Item2    15         2        30


TotalAll:90

Amount column is input tag where user can put how many items he wants to buy, and everything works as long as the user is adding items since in backend I'm doing sum total(TotalAll+=Total), the problem is when user put a smaller amount than currently entered for example for Item1 from 3 to 2 items, TotalAll will still add those 2 and value will be TotalAll:130 but it should be 70 because it's now 2 items. So how can I subtract from TotalAll when amount is reduced? In what case?

Upvotes: 0

Views: 193

Answers (2)

nemke nemke
nemke nemke

Reputation: 191

This my solution:

        totalAll = 0.0;
        List<Article> articleList = ArticleSelectDAO.selectArticles();
        for (Article a : articleList) {
        totalAll+=a.getTotal();
        }

Before i reset totalAll i have to update database with current total value per item. Then i add those articles in List, iterate over List and add value to totalAll.

Upvotes: 0

Dravidian
Dravidian

Reputation: 339

Whenever user changes the input, as long as Total value is refreshed for that item, You can reset the TotalAll value to 0 in your backend wherever you're summing all the Totals and recalculate the TotalAll value. This may sound inefficient but should work fine if you're dealing with minimal number of items.

Upvotes: 1

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