In this article, we will Explore Merging Two Maps In Dart. We perceive how to execute a demo program. We will show you how to couple of different approaches to merging two given maps in Dart in your applications.

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Table Of Contents::

Introduction

Spread Operator Method

addAll() Method

putIfAbsent() Method

Conclusion

Introduction:

There may be occasions while working with Dart and Flutter when you need to combine two maps, The following points are:

• > It could be desirable to merge two maps that have distinct characteristics for the same object. For example, you might have two maps: one with the user’s address, preferences, and history, and another with their name, phone number, and email address. These two can be joined to make a single map with all the user’s information on it.
• > Two maps that show separate data sources, like a local cache and a remote server, might be combined.
• > It can be desirable to combine two maps — for example, a default configuration and a user-defined configuration — that have various app configurations or settings.

Spread Operator Method:

This approach utilizes the spread operator (…) to merge two maps into another map. The spread operator permits you to grow the components of an iterable for this situation, the key-value pairs of the maps into another new collection.

import 'package:flutter/foundation.dart' show kDebugMode;
void main() { 
Map<String, int> map1 = {'a': 10, 'b': 20};
 Map<String, int> map2 = {'c': 30, 'd': 40, 'FlutterDevs.com': 50};

 Map<String, int> mergedMap = {...map1, ...map2};
 if (kDebugMode) { print(mergedMap);
 }
 }

One thing you should be aware of is that the value in the second map will overwrite the value in the first map if there are duplicate keys in the maps that are being merged.

When we run the application, we ought to get the screen’s output like the underneath screen Console Output.

{a: 10, b: 20, c: 30, d: 40, FlutterDevs.com: 50} 
 Process finished with exit code 0

addAll() Method:

This arrangement utilizes the addAll() technique to merge two maps. The addAll() strategy adds all the key-value pairs starting with one map and then onto the next map.

import 'package:flutter/foundation.dart' show kDebugMode;
 void main() { 
Map<String, int> map1 = {'a': 10, 'b': 20};
 Map<String, int> map2 = {'c': 30, 'd': 40, 'FlutterDevs.com': 50}; map1.addAll(map2);
 if (kDebugMode) { print(map1);
 }
 }

By adding each key-value pair from the second map, this method directly changes the first map. The value in the second map will overwrite the value in the first one if duplicate keys are present, just like in the previous solution.

When we run the application, we ought to get the screen’s output like the underneath screen Console Output.

{a: 10, b: 20, c: 30, d: 40, FlutterDevs.com: 50} 
Process finished with exit code 0

putIfAbsent() Method:

If the key is not already in the second map, the putIfAbsent() method adds the key-value pair from one map to another.

import 'package:flutter/foundation.dart' show kDebugMode; 

void main() { 

Map<String, int> map1 = {'a': 10, 'b': 20, 'c': 27};

Map<String, int> map2 = {'c': 30, 'd': 40, 'FlutterDevs.com': 50};

map1.forEach((key, value) { map2.putIfAbsent(key, () => value); 

});

if (kDebugMode) { print(map2);

}

}

More control over handling duplicate keys is offeredTwo by this solution. You can choose whether or not the value from the first map should replace the value in the second map by using the putIfAbsent() method. It does, however, necessitate repeating the initial map’s key-value pairings, which could affect performance for big maps.

When we run the application, we ought to get the screen’s output like the underneath screen Console Output.

{c: 30, d: 40, FlutterDevs.com: 50, a: 10, b: 20}
 Process finished with exit code 0

Conclusion:

In the article, I have explained the Merging Two Maps InDart; you can modify this code according to your choice. This was a small introduction to Merging Two Maps In Dart User Interaction from my side, and it’s working using Flutter.

I hope this blog will provide you with sufficient information on Trying the Merging Two Maps In Dart of your projects. We’ve covered a few methods for combining several maps into one. While selecting the best solution, take into account the details of your use case, the size of the maps, and the potential for duplicate keys. So please try it.

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