Code-free
Code-free

Swift: Pointers everywhere

Unsafety? More like FUnsafety

Russ Bishop
June 27, 2014

Edit: Updated with new information to clarify that UnsafePointer<T> expects the number of instances of T, not the size in bytes.

Today let's discuss UnsafePointer<T>. Perhaps you want to use a fancy function like OSAtomicIncrement32 to keep a running counter across threads and GCD queues, without any locking, . . .

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Swift: withUnsafePointerToElements

There is no escape, only vectors

Russ Bishop
June 26, 2014

Swift Array<T> is easily convertible to a C-style array, but much like the world of Garbage Collection, we have to be aware of object lifetimes.

A Swift Array is just a small stack-allocated header struct that points at heap-allocated memory to hold the elements. When you mutate an array, that header struct may change. If the . . .

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Swift: Manual retain/release

Old school

Russ Bishop
June 26, 2014

While creating ThreadLocalSlot<T>, I needed to call the posix posix_getspecific and posix_setspecific methods. Not only that, I needed to store an Objective-C object in a plain old void*. How can we accomplish that in Swift?

The key is Unmanaged. It contains magic sauce to let us turn an AnyObject into a COpaquePointer, which . . .

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Swift: Making Tuples Equatable

Lots of copypasta

Russ Bishop
June 23, 2014

Until we get a first-class macro system, this involves a lot of copypasta, but it does work:

@infix func == <T:Equatable> (lhs: (T), rhs: (T)) -> Bool {
 return lhs.0 == rhs.0
}

@infix func == <T:Equatable, T2:Equatable> (lhs: (T,T2), rhs: (T,T2)) -> Bool {
 return lhs.0 == rhs.0 &&
 lhs . . .

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Bigger iPhone and side-by-side iPad apps

Apple screams loudly, no one pays attention

Russ Bishop
June 23, 2014

Apple is telling us without telling us to get ready ASAP: Bigger iPhone screens and/or iPad side-by-side applications are coming and you should get ready.

The new size class mechanism and the resizable simulator are practically screaming at us to get with it.

My suggestion is to get comfortable with Auto Layout and make . . .

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Swift: Storage for extension properties

Let's get in some trouble

Russ Bishop
June 23, 2014

A little birdy told me the Swift team has stored extension properties on their roadmap, but obviously we must await some future build or even revision of the language depending on when their schedule allows for it.

In the mean time, we can use objc_setAssociatedObject and objc_getAssociatedObject to simulate it. Unfortunately this . . .

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Swift: Call by name

A blast from the past

Russ Bishop
June 23, 2014

Back when computers came with some assembly required and real men/women booted by toggling switches on the front panel, a language called Algol introduced many programmers to call-by-name parameter passing.

For many of today's languages, parameters to a function call are evaluated in the caller's context then copied to the . . .

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