Swift is a programming language for creating iOS, macOS, watchOS, and tvOS apps. Swift builds on the best of C and Objective-C, without the. Download the Swift logo to use in course materials and technical publications related to teaching, training, or describing the Swift programming language. id=swift-tour. Simple Values. Use let to make a constant and var to make a variable. The value The Swift The Swift Programming Language中文.
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It's a safe, fast, and interactive programming language that combines the best in modern language thinking with wisdom from the wider Apple engineering. Apple hosts additional resources for learning Swift—such as videos, sample code The Swift Programming Language is the authoritative reference for Swift, . Swift is a new programming language for iOS and OS X apps that builds on the best of Apple laid the foundation for Swift by advancing our existing compiler.
To access the value inside, assuming it is not nil, it must be unwrapped to expose the instance inside. April 8, Retrieved September 10, Categories allow extending classes in-place to add new functions with no need to subclass or even have access to the original source code. Retrieved Protocol-oriented Programming in Swift. Swift is designed to work with Apple's Cocoa and Cocoa Touch frameworks and the large body of existing Objective-C code written for Apple products.
The performance improvement inherent to the pass-by-value concept is such that Swift uses these types for almost all common data types, including Int and Double , and types normally represented by objects, like String and Array. To ensure that even the largest structs do not cause a performance penalty when they are handed off, Swift uses copy on write so that the objects are copied only if and when the program attempts to change a value in them.
This means that the various accessors have what is in effect a pointer to the same data storage, but this takes place far below the level of the language, in the computer's memory management unit MMU.
So while the data is physically stored as one instance in memory, at the level of the application, these values are separate, and physical separation is enforced by copy on write only if needed. A key feature of Objective-C is its support for categories , methods that can be added to extend classes at runtime.
Categories allow extending classes in-place to add new functions with no need to subclass or even have access to the original source code. An example might be to add spell checker support to the base NSString class, which means all instances of NSString in the application gain spell checking.
The system is also widely used as an organizational technique, allowing related code to be gathered into library-like extensions.
Swift continues to support this concept, although they are now termed extensions , and declared with the keyword extension. Unlike Objective-C, Swift can also add new properties accessors, types and enums to extant instances. Another key feature of Objective-C is its use of protocols , known in most modern languages as interfaces. Protocols promise that a particular class implements a set of methods, meaning that other objects in the system can call those methods on any object supporting that protocol.
This is often used in modern OO languages as a substitute for multiple inheritance , although the feature sets are not entirely similar. A common example of a protocol in Cocoa is the NSCopying protocol, which defines one method, copyWithZone , that implements deep copying on objects.
In Objective-C, and most other languages implementing the protocol concept, it is up to the programmer to ensure that the required methods are implemented in each class.
Combined, these allow protocols to be written once and support a wide variety of instances. Also, the extension mechanism can be used to add protocol conformance to an object that does not list that protocol in its definition. For example, a protocol might be declared called StringConvertible , which ensures that instances that conform to the protocol implement a toString method that returns a String. In Swift, this can be declared with code like this:.
In Swift, like many modern languages supporting interfaces, protocols can be used as types, which means variables and methods can be defined by protocol instead of their specific type:. It does not matter what sort of instance someSortOfPrintableObject is, the compiler will ensure that it conforms to the protocol and thus this code is safe. As Swift treats structs and classes as similar concepts, both extensions and protocols are extensively used in Swift's runtime to provide a rich API based on structs.
A concrete example of how all of these features interact can be seen in the concept of default protocol implementations:. This function defines a method that works on any instance conforming to Equatable , providing a not equals function. Any instance, class or struct, automatically gains this implementation simply by conforming to Equatable. As many instances gain Equatable through their base implementations or other generic extensions, most basic objects in the runtime gain equals and not equals with no code.
This combination of protocols, defaults, protocol inheritance, and extensions allows many of the functions normally associated with classes and inheritance to be implemented on value types. This concept is so widely used within Swift, that Apple has begun calling it a protocol-oriented programming language. They suggest addressing many of the problem domains normally solved though classes and inheritance using protocols and structs instead.
To aid development of such programs, and the re-use of extant code, Xcode 6 and higher offers a semi-automated system that builds and maintains a bridging header to expose Objective-C code to Swift. This takes the form of an additional header file that simply defines or imports all of the Objective-C symbols that are needed by the project's Swift code. At that point, Swift can refer to the types, functions, and variables declared in those imports as though they were written in Swift.
Objective-C code can also use Swift code directly, by importing an automatically maintained header file with Objective-C declarations of the project's Swift symbols. Not all symbols are available through this mechanism, however—use of Swift-specific features like generic types, non-object optional types, sophisticated enums, or even Unicode identifiers may render a symbol inaccessible from Objective-C.
Swift also has limited support for attributes , metadata that is read by the development environment, and is not necessarily part of the compiled code. Like Objective-C, attributes use the syntax, but the currently available set is small. One example is the IBOutlet attribute, which marks a given value in the code as an outlet , available for use within Interface Builder IB.
An outlet is a device that binds the value of the on-screen display to an object in code. Apple used to require manual memory management in Objective-C, but introduced ARC in to allow for easier memory allocation and deallocation. A references B, B references A. This causes them to become leaked into memory as they are never released. Swift provides the keywords weak and unowned to prevent strong reference cycles. Typically a parent-child relationship would use a strong reference while a child-parent would use either weak reference, where parents and children can be unrelated, or unowned where a child always has a parent, but parent may not have a child.
Weak references must be optional variables, since they can change and become nil. A closure within a class can also create a strong reference cycle by capturing self references. Self references to be treated as weak or unowned can be indicated using a capture list.
A key element of the Swift system is its ability to be cleanly debugged and run within the development environment, using a read—eval—print loop REPL , giving it interactive properties more in common with the scripting abilities of Python than traditional system programming languages. The REPL is further enhanced with the new concept playgrounds. These are interactive views running within the Xcode environment that respond to code or debugger changes on-the-fly.
If some code changes over time or with regard to some other ranged input value, the view can be used with the Timeline Assistant to demonstrate the output in an animated way. In addition, Xcode has debugging features for Swift development including breakpoints, step through and step over statements, as well as UI element placement breakdowns for app developers.
Apple says that Swift is "an industrial-quality programming language that's as expressive and enjoyable as a scripting language". Many of the features introduced with Swift also have well-known performance and safety trade-offs. Apple has implemented optimizations that reduce this overhead. Since the language is open-source, there are prospects of it being ported to the web.
An official "Server APIs" work group has also been started by Apple,  with members of the Swift developer community playing a central role. From Wikipedia, the free encyclopedia.
This article is about the Apple programming language. For the scripting language, see Swift parallel scripting language. This section may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts , without removing the technical details. June Learn how and when to remove this template message.
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Editing help is available. February Apple Inc. September 9, Retrieved March 8, Swift is proprietary and closed: It is entirely controlled by Apple and there is no open source implementation.
Archived from the original on July 14, Retrieved June 12, You can imagine that many of us want it to be open source and part of LLVM, but the discussion hasn't happened yet, and won't for some time. Chris Lattner. Retrieved June 3, The Swift language is the product of tireless effort from a team of language experts, documentation gurus, compiler optimization ninjas, and an incredibly important internal dogfooding group who provided feedback to help refine and battle-test ideas.
Of course, it also greatly benefited from the experiences hard-won by many other languages in the field, drawing ideas from Objective-C, Rust, Haskell, Ruby, Python, C , CLU, and far too many others to list.
I started work on the Swift Programming Language in July of I implemented much of the basic language structure, with only a few people knowing of its existence. A few other amazing people started contributing in earnest late in , and it became a major focus for the Apple Developer Tools group in July [ Retrieved September 25, Inner Exception. Retrieved March 10, Retrieved August 3, Ars Technica. Retrieved June 6, The Next Web. Retrieved June 2, The Verge.
Retrieved December 5, CIO Journal. The Wall Street Journal Blogs. December 3, Registration required help. Swift Forums. Retrieved November 19, Swift Evolution.
January — tecosystems". Retrieved June 2, Lay summary. Retrieved September 10, October 22, Retrieved January 23, April 8, Start on. Show related SlideShares at end. WordPress Shortcode. Published in: Full Name Comment goes here.
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Features of modern programming language embedded in Swift and discussed in depth in this material include: Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Apple laid the foundation for Swift by advancing the existing compiler, debugger, and framework infrastructure. The framework stack, built on the solid base of Foundation and Cocoa, has been modernized and standardized throughout.
Objective-C itself has evolved to support blocks, collection literals, and modules, enabling framework adoption of modern language technologies without disruption. Building from this common ground, Swift introduces many new features and unifies the procedural and object-oriented portions of the language.
Friendly to new programmers. It is the first industrial- quality systems programming language that is as expressive and enjoyable as a scripting language.
It supports playgrounds, an innovative feature that allows programmers to experiment with Swift code and see the results immediately, without the overhead of building and running an app. Swift combines the best in modern language thinking with wisdom from the wider Apple engineering culture.
The compiler is optimized for performance, and the language is optimized for development, without compromising on either.
Software products powered by Swift are among the best in the market offering rich user experience, security, unequalled graphics and free from virus attacks. With an exponential growth of developers in the open source community coupled with research funding from Apple and many other contributors to expand the swift library to make it more powerful, Swift is the programming language of the future.
It is built with the open source LLVM compiler framework and has been included in Xcode since version 6. However it supports many core concepts that are associated with Objective-C, notably dynamic dispatch, widespread late binding, extensible programming and similar features.
For safety, Swift helps address common programming errors like null pointers, and provides syntactic sugar to avoid the pyramid of doom that can otherwise result.
More fundamentally, Swift adds the concept of protocol extensibility, an extensibility system that can be applied to types, structs and classes.
It underwent an upgrade to version 1. Initially a proprietary language, version 2. In March , less than three years after its official debut, Swift made the top 10 in the monthly TIOBE index ranking of popular programming languages.
Feature rich enumeration II. Type Inference III. Shorthand argument names V. At the time of this writing some major improvements might have been added and some features might have also been removed to the language thus rendering some topics, features and constraints mentioned in this material null. Multi-paradigm languages can always have the problem of redundancy. Operator overloading and custom operators are controversial features of the Swift language, this impedes performance and inconsistency in operator declaration and use.
Swift has been said to suffer from redundancy due to compatibility issues. Before you can write Swift codes or develop efficient programs using Swift language the hardware and software must be compatible in most cases only Apple powered operating systems are compatible though there is recent support for Linux operating systems.
Basically Swift only supports Apple and Linux environments with other dependencies not to be mentioned here. Nonetheless, many parts of Swift will be familiar from your experience of developing in C and Objective-C. Swift provides its own versions of all fundamental C and Objective-C types, including Int for integers, Double and Float for floating-point values, Bool for Boolean values, and String for textual data.
Swift also provides powerful versions of the three primary collection types, Array, Set, and Dictionary. Like C, Swift uses variables to store and refer to values by an identifying name. Swift also makes extensive use of variables whose values cannot be changed. These are known as constants, and are much more powerful. Constants are used throughout Swift to make code safer and clearer in intent when you work with values that do not need to change.
In addition to familiar types, Swift introduces advanced types, such as tuples. Tuples enable you to create and pass around groupings of values. You can use a tuple to return multiple values from a function as a single compound value.
Swift also introduces optional types, which handle the absence of a value. Using optionals is similar to using nil with pointers in Objective-C, but they work for any type, not just classes.
Swift is a type-safe language, which means the language helps you to be clear about the types of values your code can work with. If part of your code expects a String, type safety prevents you from passing it an Int by mistake. Likewise, type safety prevents you from accidentally passing an optional String to a piece of code that expects a nonoptional String. Type safety helps you catch and fix errors as early as possible in the development process.
A beta version of the programming language was released to registered Apple developers at the conference, but the company did not promise that the final version of Swift would be source code compatible with the test version.
Apple planned to make source code converters available if needed for the full release. Swift reached the 1. Swift 1. Swift 2. Swift 3.
In December , IBM announced its Swift Sandbox website, which allows developers to write Swift code in one pane and display output in another. The app is presented in a 3D video game-like interface which provides feed back when lines of code are placed in a certain order and executed.
September 9, Retrieved March 8, In Swift, this can be done in a single line: Code written at global scope is used as the entry point for the program, so no need for a main function. In Swift also there is no need to write semicolons at the end of every statement. Use let to make a constant and var to make a variable. The value of a constant does not need to be known at compile time, but a value must be assigned to it exactly once.
This means constants can be used to name a value determined once but use in many places. Providing a value when you create a constant or variable lets the compiler infer its type. Swift is an alternative to the Objective-C language that employs modern programming-language theory concepts and strives to present a simpler syntax. Swift introduces true named parameters and retains key Objective-C concepts, including protocols, closures and categories, often replacing former syntax with cleaner versions and allowing these concepts to be applied to other language structures, like enumerated types enums.
Unlike many object-oriented languages, these access controls ignore inheritance hierarchies: This implies that non-optional types cannot result in a null-pointer error; the compiler can ensure this is not possible. Optional types are created with the Optional mechanism—to make an Integer that is nullable, one would use a declaration similar to var optional Integer: As in C , Swift also includes syntactic sugar for this, allowing one to indicate a variable is optional by placing a question mark after the type name, var optional Integer: Variables or constants that are marked optional either have a value of the underlying type or are nil.
Optional types wrap the String and String? To access the value inside, assuming it is not nil, it must be unwrapped to expose the instance inside. This is per- formed with the! If an Optional Instance is nil, a null- pointer error occurs.
This can be annoying in practice, so Swift also includes the concept of optional chaining to test whether the instance is nil and then unwrap it if it is non-null: Normally this requires the programmer to test whether my Value is nil before proceeding. For instance: Tenant List. Lease Details?. Swift 2 introduced the new keyword guard for cases in which code should stop executing if some condition is unmet: Tenant List?. While the syntax can act as an if statement, its primary benefit is inferring non- null ability.
Where an if statement requires a case, guard assumes the case based on the condition provided. This is performed with the keywords return, continue, break, or throw. ObjC was weakly typed, and allowed any method to be called on any object at any time. If the method call failed, there was a default handler in the runtime that returned nil. That meant that no unwrapping or testing was needed, the equivalent statement in ObjC: However, this also demanded that all method calls be dynamic, which introduces significant overhead.
Objects are passed between methods by copying the value of the pointer, In contrast, basic types like integers and floating point values are represented directly; the handle contains the data, not a pointer to it, and that data is passed directly to methods by copy- ing.
These styles of access are termed pass-by-reference in the case of objects, and pass-by-value for basic types. Both concepts have their advantages and disadvantages. Objects are useful when the data is large, like the description of a window or the contents of a document. In these cases, access to that data is provided by copying a or bit value, versus copying an entire data structure. However, smaller values like integers are the same size as pointers typically both are one word , so there is no advantage to passing a pointer, versus passing the value.
Also, pass-by-reference inherently requires a dereferencing operation, which can produce noticeable overhead in some operations, typically those used with these basic value types, like mathematics. Similarly to C and in contrast to most other OO languages, Swift offers built-in support for objects using either pass-by-reference or pass-by-value semantics, the former using the class declaration and the latter using struct.
Structs in Swift have almost all the same features as classes: For this reason, Apple terms all data generically as instances, versus objects or values. Structs do not support inheritance, however. The programmer is free to choose which semantics are more appropriate for each data structure in the application. Larger structures like windows would be defined as classes, allowing them to be passed around as pointers.