Скачать или смотреть Extracting Int Values from NSData in Objective-C

Learn how to extract integer values from `NSData` in Objective-C with a practical example involving parsing real-time data from a BTLE device.
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This video is based on the question https://stackoverflow.com/q/63562325/ asked by the user 'Ultra_charge' ( https://stackoverflow.com/u/3511442/ ) and on the answer https://stackoverflow.com/a/63562580/ provided by the user 'matt' ( https://stackoverflow.com/u/341994/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Extracting Int Values from NSData in Objective-C

When working with data from Bluetooth Low Energy (BTLE) devices, it can be challenging to pull out the specific information you need from NSData objects. If you’ve found yourself in a situation where you need to extract individual integer values from NSData, this post will guide you through an effective solution.

Understanding the Problem

You are using a library that transfers data from a BTLE device into an NSData format. The task is to extract individual integer values to display them in your app. Let's walk through a code example you have, which demonstrates this process.

Example Code

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

Parsing the Data

To extract individual integer values, you should first check if the VTRealObject, created from your parsed data, already contains the values you wish to display. If it does, accessing them is straightforward.

Extracting Properties

The VTRealObject contains multiple properties, including:

Blood oxygen value (spo2)

Heart rate (hr)

Battery value (battery)

Battery status (batState)

Perfusion Index value (pi)

Lead status (leadState)

Motion value (vector)

You can simply access these properties as shown below:

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

Each of these variables can now be assigned to individual labels in your user interface.

If Individual Values Are Not Available

If you find that the properties do not contain the data you require or you need to dig into the raw data format, you'll have to parse the realData manually. Here's how to approach this:

Understand the Data Format: Know the layout of realData. For example, if certain bytes correspond to specific properties like batState, make sure to identify their positions.

Extracting Data: You can read the bytes from NSData as integers. Here is an example of how to accomplish this:

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

Make sure you adapt the offset values (0, 1, 2, ..., n) based on the actual format of realData.

Conclusion

Extracting integer values from NSData in Objective-C is achievable with a solid understanding of both the data structure and your objectives. Checking for properties within your parsed object is often the most convenient method, but don’t hesitate to dive into the raw bytes if necessary. With this knowledge, you can now assign the values to individual labels in your application easily.



If you encounter any further questions or require additional assistance, feel free to reach out!