Dealing With Asynchrony in a Synchronous Swift World How do we deal with Swift code that executes in a mostly straight line when there are so many side tangents and threads to wait around for? Operators and Strong Opinions Swift operators are flexible and powerful, but only when they are well-chosen and heavily used. About the content This content has been published here with the express permission of the author.
More on similar topics
Realm Team At Realm, our mission is to help developers build better apps faster. Featured News.
- Cost Modelling (Foundations of Building Economics Series);
- Handbook of Asset and Liability Management: From Models to Optimal Return Strategies (The Wiley Finance Series).
- The Edge of Desire (Bastion Club, Book 7);
- Patterns in Protein Sequence and Structure.
- CBS Sports Presents : Stories From the Final Four!
- Advanced Swift, fourth edition.
- Advanced Swift – Ole Begemann.
Offline experience issues with the travel See more. Thanks for subscribing You will be receiving an email shortly with details on your subscription. Oops something went wrong You will not be receiving an email shortly with details on your subscription. We can get the pointer for the object, and then run an expression in Objective-C:.
Reading Private Instance Variables. In modern Objective-C, properties are much more common than instance variables; we can simply use the above technique to run the private getter or setter methods backing the property. However, in UIKit, instance variables without properties are common and so are much harder to debug. This property appears to be set whenever a cell in UITableView becomes the first responder.
However, nothing is really private in Objective-C.
Advanced Swift Protocols
We can use the runtime to access any instance variable, even if it is private. First, we need to query the class for the Ivar object. Then we can query the instance for the value of this instance variable:. It is useful to call and read private methods, but it is often more useful to see when these values change. Swizzling allows us to add breakpoints, examine the stack, and get clues on how features are implemented. We want to know when a property on an object is changing. The easiest way to do this is to swizzle the setter.
Swizzling is an Objective-C runtime technique to exchange method implementations. We replace the existing method with a new method, print the new value, and then call the old method. We effectively insert some debug code between the call site and the actual implementation of the method. It looks like this:. In this case, we wanted to know when the minimum zoom scale changed.
- Hausa stories and riddles, with notes on the languages etc., - and a concise - Hausa dictionary.
- Handbook of Veterinary Pain Management, 3e.
- Mastering VMware vSphere 6.
Whenever setMinimumZoomScale is called, the breakpoint will hit. We will then have a full stack trace to examine where and why the zoom scale changed. Swizzling Private Methods. We just create an Objective-C category on the object and add it to the interface. If we want to know when a property changes, we can simply swizzle the setter.
However, many UIKit variables are not backed by properties but are instead set directly. We can listen to any variable with the watchpoint command in lldb:.
Review: Swift Playgrounds for iPad | Swift by Sundell
In particular, they're great tools to clearly manifest the intentions of your code. In this post, we'll first look at the syntax and possibilities of using enum , and will then use them in a variety of hopefully practical, real world scenarios to give a better idea of how and when to use them. We'll also look a bit at how enums are being used in the Swift Standard library. Before we dive in, here's a definition of what enums can be. We'll revisit this definition later on:.