Скачать или смотреть How to Check if an Array Contains Another Array in DART/Flutter and Find Its Position

Learn how to effectively check if an array contains another array in DART and Flutter. Discover a custom function to find the exact position of the inner array.
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This video is based on the question https://stackoverflow.com/q/69513913/ asked by the user 'omar' ( https://stackoverflow.com/u/12130011/ ) and on the answer https://stackoverflow.com/a/69513928/ provided by the user 'Morteza Mohammadi' ( https://stackoverflow.com/u/16779388/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Check if an Array Contains Another Array in DART/Flutter and Find Its Position

In the world of programming with DART and Flutter, working with arrays (or lists as they are called in DART) is a common task. A frequent challenge is determining if one array contains another array and, if it does, identifying the exact position of that inner array. In this guide, we'll address this issue and provide a practical solution.

The Problem

Imagine you have a main list of arrays (or lists) like this:

[[See Video to Reveal this Text or Code Snippet]]

You want to check if a specific inner array, say [1, 1], exists in the main list and, if it does, return its position. You might be inclined to use the indexOf method to achieve this. However, you may find yourself perplexed when indexOf returns -1, indicating that the array was not found.

Why indexOf Doesn't Work Here

The indexOf function in DART checks for the reference (or identity) of elements, not their individual content. When working with lists of lists, indexOf does not compare the contents of the inner lists, leading to unexpected results.

A Custom Solution

To solve this problem, we need to create a custom function that can thoroughly compare each inner list's contents to the target array. Below is the function you can use:

[[See Video to Reveal this Text or Code Snippet]]

How the Function Works

Parameters:

The function takes two parameters:

list: A list of lists (the main list).

element: The list we are searching for.

Outer Loop:

We loop through each element of the main list using a for loop.

Length Check:

A check is performed to see if the length of the current inner list matches the length of the element we are searching for. If not, we skip this iteration.

Inner Loop:

We then compare each individual item in the current inner list with the corresponding item in the target array.

If any items do not match, we set a rejected flag to true.

Return the Index:

If no mismatches are found (rejected stays false), we return the index (i) of the matched inner list.

Not Found:

If the outer loop completes without finding a match, we return -1.

Example Usage

Here's how you can use the function in practice:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Checking if an array contains another array in DART and Flutter isn't directly achievable with the native indexOf method due to its limitations with nested lists. However, by implementing a custom comparison function, you can accurately find the position of any inner array.

Now you're equipped with the knowledge to tackle this challenge effectively. Happy coding!