Properties are an important aspect of working with Objective-C. In this video, you'll learn how to use properties with your Objective-C code.
A declared property provides a syntactical shorthand for declaring a class’s accessor methods and, optionally, implementing them. You can declare a property anywhere in the method declaration list, which is in the interface of a class, or in the declaration of a protocol or category.
You begin a property declaration with the keyword @property. You can then optionally provide a parenthesized set of property attributes that define the storage semantics and other behaviors of the property. (Refer to the document that definitively describes property lists for descriptions of these attributes.)
Each property declaration ends with a type specification and a name.
In addition to declaring the accessor methods, you can instruct the compiler to synthesize implementations of them (or inform the compiler that your class will synthesize them at runtime).
You use the @synthesize statement in a class’s implementation block to tell the compiler to create implementations that match the specification you gave in the property declaration.
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About Objective C (from Wikipedia)
Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It was the main programming language used by Apple for the OS X and iOS operating systems, and their respective application programming interfaces (APIs) Cocoa and Cocoa Touch prior to the introduction of Swift.
The programming language Objective-C was originally developed in the early 1980s. It was selected as the main language used by NeXT for its NeXTSTEP operating system, from which OS X and iOS are derived. Portable Objective-C programs that do not use the Cocoa or Cocoa Touch libraries, or those using parts that may be ported or reimplemented for other systems, can also be compiled for any system supported by GNU Compiler Collection (GCC) or Clang.
Objective-C source code 'implementation' program files usually have .m filename extensions, while Objective-C 'header/interface' files have .h extensions, the same as C header files. Objective-C++ files are denoted with a .mm file extension.
In computer science and computer programming, a data type or simply type is a classification of data which tells the compiler or interpreter how the programmer intends to use the data. Most programming languages support various types of data, for example: real, integer or Boolean. A Data type provides a set of values from which an expression (i.e. variable, function ...) may take its values. The type defines the operations that can be done on the data, the meaning of the data, and the way values of that type can be stored.
Data types are used within type systems, which offer various ways of defining, implementing and using them. Different type systems ensure varying degrees of type safety.
Almost all programming languages explicitly include the notion of data type, though different languages may use different terminology. Common data types include:
For example, in the Java programming language, the "int" type represents the set of 32-bit integers ranging in value from -2,147,483,648 to 2,147,483,647, as well as the operations that can be performed on integers, such as addition, subtraction, and multiplication. Colors, on the other hand, are represented by three bytes denoting the amounts each of red, green, and blue, and one string representing that color's name; allowable operations include addition and subtraction, but not multiplication.
Most programming languages also allow the programmer to define additional data types, usually by combining multiple elements of other types and defining the valid operations of the new data type. For example, a programmer might create a new data type named "complex number" that would include real and imaginary parts. A data type also represents a constraint placed upon the interpretation of data in a type system, describing representation, interpretation and structure of values or objects stored in computer memory. The type system uses data type information to check correctness of computer programs that access or manipulate the data.