How to Access All Objects from a C-Array's Pointer of Different NSObjects in Swift and Objective-C

Описание: Learn how to effectively access all objects in a C-array of `NSObjects` by creating a wrapper struct for better memory management in Objective-C and Swift.
---
This video is based on the question https://stackoverflow.com/q/67780202/ asked by the user 'Alexandr Dorofeev' ( https://stackoverflow.com/u/5655202/ ) and on the answer https://stackoverflow.com/a/67807250/ provided by the user 'Alexandr Dorofeev' ( https://stackoverflow.com/u/5655202/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to get all objects from the C-array's pointer of different NSObjects?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Accessing All Objects from a C-Array's Pointer of Different NSObjects

When dealing with Objective-C and Swift, accessing hidden instance variables may sometimes present challenges. This is particularly true when working with C-style arrays and the NSObjects they contain. In this guide, we will walk through how to successfully access all the objects from a C-array's pointer, explaining both the issue and the solution in detail.

Understanding the Problem

In certain instances in Objective-C, you might encounter a situation where you need to get access to a hidden instance variable that contains a pointer to an array of NSObjects. The challenge arises when you attempt to navigate through this pointer to access the actual objects themselves. Below are key points regarding the problem:

Hidden Instance Variables: These are defined with type encodings like [3@ ], indicating that the variable is an array of three different NSObjects.

Pointer Arithmetic Limitations: Simple pointer arithmetic does not work seamlessly with NSObject, which can lead to confusion and errors such as EXC_BAD_ACCESS.

Given the complexity of C pointers, let's explore the solution to this problem.

The Solution: Creating a Wrapper Struct

The effective way to retrieve the objects you need is to create a wrapper struct that matches the number of elements in the C-array. Here’s how you can implement the solution:

Step 1: Define the Wrapper Struct

Create a struct that contains pointers for each object you wish to retrieve from the array. Here is an example implementation:

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

Step 2: Access the Array

Next, implement a method to retrieve the reserved array. This method will make use of the previously defined struct.

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

In this code snippet:

getIvar: retrieves the instance variable using its name.

The function calculates the correct offset and dereferences it to return the reservedArray.

Step 3: Create a Trace Method

Finally, implement a trace method that calls your getReservedArray: method to return the array of objects.

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

Considerations for Swift

If you’re working with Swift, the process is similar but requires careful memory management due to Swift’s stricter type system. Here is how you can convert the pointer to an array:

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

In the Swift implementation, ensure to handle the instance safely and validate the size of the memory being accessed.

Conclusion

Accessing objects from a C-array's pointer of NSObjects can seem daunting due to the intricacies of pointer arithmetic and type management. However, by creating a wrapper struct to encapsulate the pointers and leveraging the Objective-C runtime features effectively, you can simplify the process significantly.

Now you have a clear and actionable way to access all objects from C-array pointers, enhancing your ability to work with low-level data in Swift and Objective-C. If you've encountered similar issues or have further questions, feel free to reach out or leave a comment!