Objective-C for Swift Developers


Do you hold the common vision that Objective-C isn’t in Apple’s future? Limit blank lines to one or two between functions and between logical groups of code. To allow more code to be easily viewed on a screen, avoid putting blank lines just inside the braces of functions. When updating legacy code, consider also breaking long functions into smaller and more manageable pieces. Continuation lines for function parameters may be indented to align with the opening parenthesis, or may have a four-space indent. The open curly brace is always on the end of the last line of the function declaration, not the start of the next line.

Delegates, target objects, and block pointers should not be retained when doing so would create a retain cycle. Also, don’t directly compare BOOL variables directly with YES. Not only is it harder to read for those well-versed in C, but the first point above demonstrates that return values may not always be what you expect. Avoid nil pointer checks that exist only to prevent sending messages to nil. Sending a message to nil reliably returnsnil as a pointer, zero as an integer or floating-point value, structs initialized to 0, and _Complex values equal to .

Objective-C explained

All the compiler can do is intelligently analyze your code to see if you might be making a mistake that could matter at runtime. Using id turns off this part of the compiler’s intelligence and leaves you to your own devices. Whether this behavior of Objective-C is a good thing is a quasi-religious issue and a subject of vociferous debate among programmers. It is useful, but it is also extremely easy to be tricked by it.

Objective-C uses the runtime code compilation

Objective C is a super-set of C language with object-orientation and other new features. Overall, Swift improves code readability and maintainability. Introduced in 1979, Wilkerson says that C++ was explicitly designed to combine objects and instance methods to the original C language. Using blocks, there is no need to adopt protocols, or implementing delegate methods that lead to much more code in a class.

However, what we have not seen yet, is how we call blocks, as just simply declaring and defining them has no meaning at all. Blocks have just one weird characteristic, and that’s the way they are written. If you are new to all these, don’t worry, as after a couple of days of using and writing blocks, you will get used to it like everything else in Objective-C. Dynamic linking is performed by the dynamic linker (dyld on MacOS/iOS). The dynamic linker will load a binary file to memory and find the dynamic dependencies of the binary. Effectively, dynamic linking happens between two binary files.

We just add the two numbers, and we call the completion handler, passing the expected parameter, the result of the addition. Through this really simple example, the use of __block specifier becomes as much clear as it can get. As a final note, when you use it, don’t forget when to type two underscore symbols before the block keyword. As you see, the return type of the block is void, so there is no return command.

How Rewriting a C++/ObjC Codebase in Swift Shrank it down to 30% – InfoQ.com

How Rewriting a C++/ObjC Codebase in Swift Shrank it down to 30%.

Posted: Sun, 10 Jul 2022 07:00:00 GMT [source]

Some declaration attributes accept arguments that specify more information about the attribute and how it applies to a particular declaration. These attribute arguments are enclosed in parentheses, and their format is defined by the attribute they belong to. In pure C code, you will sometimes see a pointer-to-nothing expressed as NULL. NULL and nil are functionally equivalent nowadays, and I’ll use nil exclusively in this book. Thirdly, if you need complex work with the network, memory, device resources, then you have to use languages ​​\u200b\u200bwith a lower level of abstraction than Swift. It can be Objective-C, Objective-C++, or just C and C++, depending on how low level we want.


This shows that the metadata contains all the information needed to fully reconstruct the original class declarations. Apply this attribute to the type of a function to indicate that the function or closure is sendable. Applying this attribute to a function type has the same meaning as conforming a non–function type to the Sendable protocol. The function value carries no context and uses the C calling convention.

Objective-C explained

You can call an instance of a dynamically callable type as if it’s a function that takes any number of arguments. Anything that is declared in a .m file is not visible to other source files, because you typically do not import .m files . Nevertheless, the declaration still exist – just the compiler does not know of it when compiling the other file. Thus, id is a device for turning off the compiler’s type checking altogether. Concerns about what type an object is are postponed until the program is actually running.

It does this by leveraging front-end web design technologies like HTML5, CSS, React, and Angular to render apps on a browser called a WebView. The other is that Flutter is compiled ahead of time instead of using a runtime environment like RN. It simplifies your project by requiring you only to use JavaScript, one of the most popular and widely used languages today. Still, unless you’re writing high-performance Android apps where latency is critical, it’s best to stick with Java or Kotlin over C/C++. With the direction Google is taking with Kotlin, it’s a worthwhile language for future-proofing your next project. What started as an improvement over many of Java’s limitations is now Google’s preferred language for Android development, further cementing Kotlin as a viable Java alternative.

Objective-C memory management within the Cocoa API

First of all, we are going to create some code that will display messages only on the debugger, without build any special UI for it. That’s because we’ll focus on making our debut in writing blocks, and that part will consist of multiple, small examples, for which we care about only for the returned results. https://globalcloudteam.com/ However, we’ll do some interface building as well, as we are going to perform some view-related tasks and we want our application to provide UI interaction. The most important is that each part of our app will focus on another way of using blocks, so useful techniques to be demonstrated in practice.

Objective-C explained

Out-Of-the-box mobile app solutions Recognized as a top mobile development specialist. Nevertheless, if you’re coming from .NET, Xamarin is your fastest route to mobile app development. Companies that use Xamarin include BBVA, UPS, and Alaska Airlines. It allows you to create apps using C# and deploy them across platforms, including iOS, Android, and Windows. RN works by taking code written in Javascript and compiling it into native OS code, allowing developers to reuse up to 90% of the codebase across platforms for better consistency. It’s also closer to the underlying hardware than other languages, giving you complete control over device-specific functions and resources.

Objective-C Method Names

As this analysis illustrates, the average size of a Flutter APK is among the biggest compared to RN, Java, and Kotlin apps. Compared to React Native, Flutter offers several distinct improvements. The most crucial is that it draws UI components directly on each native OS, unlike RN or Xamarin that relies on platform-specific UI libraries.

  • In the Objective-C example, the way of coding , with the square brackets, is very unique.
  • And also how Swizzling works, what a Selector is, how the responder chain works, and so on.
  • For example, Objective-C helps to understand that not all NSProxy is NSObject and what is the difference between Int, NSInteger and NSNumber.
  • Delegates, target objects, and block pointers should not be retained when doing so would create a retain cycle.

However, React Native still isn’t as fast as a true native app. It also has built-in support for Flipper , giving app developers a suite of debugging and testing tools. Kotlin is both expressive and concise, allowing developers to produce shorter, easier-to-maintain code. One area where Kotlin is a step-up from Java is the latter’s tendency to write boilerplate – or unnecessarily long – code.

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Procedural programming has no other way of reusing a piece of code multiple times, and no way of organizing code more sensibly. A better way of organizing your code is called Object-Oriented Programming or OOP. Swift is easier to learn than Objective-C, it has a powerful syntax and it’s widely used for iOS, macOS, tvOS, watchOS and iPadOS apps. Swift is open source and supported on Linux and Windows (5.3-6), which means it has the power to break free from the Apple ecosystem.

Objective-C explained

__attribute__ is an approved exception, as it is used in Objective-C API specifications. In Doxygen-style comments, prefer demarcating symbols with a monospace text command, such as @c. End-of-line comments should be separated from the code by at least 2 spaces.

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Let’s see a quite simple example on how we can create a method with a completion handler, how we call it and how to deal with the completion handler. To keep it simple, we will implement a method which adds two integers, and instead of returning ios swift vs objective c the result to the caller, it will send it back using the completion handler. Of course, in real life you’ll never create such a simple method using a completion handler, but I’m confident that will help everyone to get the whole idea.

Objective-C Fundamentals

Apply this attribute to the type of a function to indicate its calling conventions. Apply this attribute to a protocol type as part of a type declaration’s list of adopted protocols to turn off enforcement of that protocol’s requirements. Isn’t available at runtime, even in the case where that type is explicitly not being used. Attribute tells the compiler to make the declaration unavailable in Objective-C code, even though it’s possible to represent it in Objective-C. When compiling ClassC.m, the compiler get’s to know that someting like aInt exists in ClassA. The linker – as the final step – then checks if this really is true, e.g. if one of the compiled source files contained the definition of aInt.

If an id’s ability to receive any message reminds you of nil, it should. I have already said that nil is a form of zero; I can now specify what form of zero it is. Defined somewhere in your code, even though it isn’t an NSString method, ARC now takes its hands off the tiller entirely, and permits the program to compile and run without warning. You are now sending a message to an id, and an id can legally receive any message. If you crash at runtime, that’s your problem; ARC can’t save you from yourself. This is possible because instances can have instance variables that point to other objects, and those pointers can persist as long as the instances themselves do.

This is the purpose we own the ‘NS’ prefix for the class in the Foundation Framework and the ‘UI’ prefix for the classes in UIKit. This reference has been prepared for the beginners to help them understand the basic to advanced concepts related to Objective-C Programming languages. After Swift was going open source, representatives of three leading corporations – Google, Facebook, and Uber – conducted a meeting in London to discuss a new language.

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