Tonally distinct in ways that highlight the dark secrets and dangers as well as the hope, The AM Archives opens up with a look into the ongoing movements of a monitoring agency for people with superhuman powers.
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While old-time fans will get to hear Dr. Note: this show is available for free with a Luminary trial. In The Record , the creators of the amazing audio drama, Joseph , have crafted a pre-apocalyptic narrative with an interesting set of characters, an interesting premise, and characteristically excellent sound design. If you really loved Joseph , then you will love this as well. The History of Aotearoa New Zealand is in its early stages and is currently a mixture of legend, fact, and excellent storytelling.
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Polybius is back. This time, it is an indie audio drama, and it is, as always, mysterious and fun. Middle America is a combination of original music, history, and personal journal that makes unexpected connections between kids in midwest suburbia and gangsters during Prohibition. Host Katherine Goldstein of The Double Shift made an excellent audio diary on not having it all as her personal and professional lives collided while covering the working mom beat. Brendan Hutchins and Mark Steadman, along with a slew of guests, delve into many elements of podcast burnout during a limited run series for Bitrate.
The Last Days of August , an Audible original, is now available on all apps. One of my favorite things to do while I listen is sew or knit, or crochet, or embroider… , so I was happy to stumble upon Reverberate , a show about textile makers. This show comes to us from the Oakland, CA, textile shop and studio A Verb for Keeping Warm, and each episode features an interview with a different person in the fiber community.
I particularly liked the episode with artist and teacher Youngmin Lee , who talks about her work making Korean wrapping cloths. The first season of The Pledge profiles six women in Alabama who are working create change in their communities. One ran to become the first African American judge in an all-white judicial system, another visits community hangouts to encourage her neighbors to speak out, and others train and campaign for the candidates they support.
You can see this in the following code:. It uses sorted , so it restricts T to types that conform to Comparable. Rewrite this function as an extension method on Array so that you can write something like this:. Note that the new method is available only when the generic Element type conforms to Comparable. Here's a function to divide two optional doubles. There are three preconditions to verify before performing the actual division:.
Improve this function by using the guard statement and without using forced unwrapping. The guard statement introduced in Swift 2.
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It's very helpful when checking preconditions because it lets you express them in a clear way — without the pyramid of doom of nested if statements. Here is an example:. You can also use the guard statement for optional binding, which makes the unwrapped variable accessible after the guard statement:.
Notice the absence of the implicitly unwrapped operators on the last line because you've unwrapped both dividend and divisor and stored them in non-optional immutable variables. Note that the results of the unwrapped optionals in a guard statement are available for the rest of the code block that the statement appears in.
The if let statement lets you unwrap optionals and use the value within that code block. Note that you cannot access the unwrapped optional outside the block. You can write the function using an if let statement such as:. A const is a variable initialized at compile time with a value or an expression that must be resolved at compilation time. An immutable created with let is a constant determined at runtime. You can initialize it with a static or a dynamic expression. This allows a declaration such as:.
To declare a static property or function, you use the static modifier on value types. Here's an example for a structure:. For classes, it's possible to use either the static or the class modifier. They achieve the same goal, but in different ways. Can you explain how they differ?
Using class lets you override the property or function.
For example, in this code the compiler will complain when you try to override illuminate :. No, it's not possible.
You can use an extension to add new behavior to an existing type, but not to alter either the type itself or its interface. If you add a stored property, you'd need extra memory to store the new value. An extension cannot manage such a task. A protocol is a type that defines a blueprint of methods, properties and other requirements. A class, structure or enumeration can then adopt the protocol to implement those requirements. A type that adopts the requirements of a protocol conforms to that protocol. The protocol doesn't implement any functionality itself, but rather defines the functionality.
You can extend a protocol to provide a default implementation of some of the requirements or additional functionality that conforming types can take advantage of. Swift defines protocols that enable you to initialize a type with literal values by using the assignment operator. Adopting the corresponding protocol and providing a public initializer allows literal initialization of a specific type.
Swift has a set of pre-defined operators to perform arithmetic or logic operations. It also allows the creation of custom operators, either unary or binary. The declaration uses the operator keyword to specify the type unary or binary , the sequence of characters composing the operator, its associativity and precedence. Swift 3. There is no predefined standard precedence for exponential operations in Swift. So you'll need to create a custom precedence that places them higher than multiplication. Note that since the code doesn't take overflows into account, if the operation produces a result that Int can't represent, such as a value greater than Int.
Consider the following code that defines Pizza as a struct and Pizzeria as a protocol with an extension that includes a default implementation for makeMargherita :. The following code creates two instances of Lombardi's. Which of the two will make a margherita with basil? They both do. The Pizzeria protocol declares the makeMargherita method and provides a default implementation. The Lombardis implementation overrides the default method. Since you declare the method in the protocol in both cases, you'll invoke the correct implementation at runtime.
What if the protocol doesn't declare the makeMargherita method but the extension still provides a default implementation, like this? Here, only lombardis2 would make the pizza with basil, whereas lombardis1 would make a pizza without it, because it would use the method defined in the extension. The following code has a compile time error.
Can you spot it and explain why it happens? What are some ways you could fix it? The else block of a guard requires an exit path, either by using return , throwing an exception or calling a noreturn. The easiest solution is to add a return statement.
Finally, here's an implementation calling fatalError , which is a noreturn function. Closures are reference types.
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If you assign a closure to a variable and you copy the variable into another variable, you also copy a reference to the same closure and its capture list. You use the UInt type to store unsigned integers. It implements the following initializer to convert from a signed integer:. However, the following code generates a compile time error exception if you provide a negative value:.
An unsigned integer by definition cannot be negative. However, it's possible to use the memory representation of a negative number to translate to an unsigned integer. How can you convert an Int negative number into an UInt while keeping its memory representation? A circular reference happens when two instances hold a strong reference to each other, causing a memory leak because neither of the two instances will ever be deallocated.
The reason is that you cannot deallocate an instance as long as there's a strong reference to it, but each instance keeps the other alive because of its strong reference. You'd solve the problem by breaking the strong circular reference by replacing one of the strong references with a weak or an unowned reference.
Swift allows the creation of recursive enumerations. Here's an example of such an enumeration with a Node case that takes two associated value types, T and List :. Some of these questions are pretty complicated.