Скачать или смотреть Merging Two Lists of Objects in Dart

Learn how to effectively merge two lists of objects in Dart by eliminating duplicates and summing their parameters. Our guide walks you through the process with easy-to-understand examples.
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Merging Two Lists of Objects in Dart: A Step-by-Step Guide

When developing apps in Dart, especially with Flutter, you may come across a situation where you need to merge lists of objects while ensuring duplicates are handled correctly. Imagine you have a list of Person objects, each with a name and a counter. Some names can appear more than once, and your goal is to merge these duplicates by summing their counters instead of just keeping separate entries. This guide will walk you through how to accomplish this in a clear and straightforward manner.

Understanding the Problem

Let’s say you have the following Person class:

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You create a list and add several Person objects to it, some with the same name:

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Your task is to merge the entries so that there is only one Person object for "Ben," and the counter is the sum of the two counters, resulting in a single object with counter equal to 7.

The Solution

To solve this merging problem, we can create an extension method on the list of Person objects. Here’s how we can approach the solution step-by-step.

Step 1: Define the Person Class

The first step is defining our Person class correctly. We want our constructor to require name and counter parameters, and we should also mark the properties as final if they won’t change after instantiation.

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Step 2: Create an Extension for the List

Next, we need to implement an extension on the List<Person>. This extension will provide a custom method to add a new person to the list while handling duplicates. Here’s how you can structure it:

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Step 3: Use the List in Your Main Function

Now we can create our list and use the addPerson method to handle adding Person objects:

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Example Output

When the above code executes, you will see:

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This confirms that the duplicates were merged correctly, and "Ben" now has a combined counter of 7.

Conclusion

Merging lists while managing duplicates is a common task in Dart programming. By utilizing extensions, we can create powerful, reusable methods that simplify our code and enhance the functionality of our lists. Now, you can easily manage lists of objects in Dart, ensuring your data remains clean and meaningful. Happy coding!