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A delegate is a common design pattern used in Cocoa and CocoaTouch frameworks, where one class delegates responsibility for implementing some functionality to another. This follows a principle of separation of concerns, where the framework class implements generic functionality while a separate dele...

One method is available for counting the number of occurrences of a sub-string in another string, str.count. str.count(sub[, start[, end]]) str.count returns an int indicating the number of non-overlapping occurrences of the sub-string sub in another string. The optional arguments start and end ...

Routes are defined in config/routes.rb. They are often defined as a group of related routes, using the resources or resource methods. resources :users creates the following seven routes, all mapping to actions of UsersController: get '/users', to: 'users#index' post '/users', ...

Signed integers can be of these types (the int after short, or long is optional): signed char c = 127; /* required to be 1 byte, see remarks for further information. */ signed short int si = 32767; /* required to be at least 16 bits. */ signed int i = 32767; /* required to be at least 16 bits */ ...

A string literal in C is a sequence of chars, terminated by a literal zero. char* str = "hello, world"; /* string literal */ /* string literals can be used to initialize arrays */ char a1[] = "abc"; /* a1 is char[4] holding {'a','b','c','\0'} */ char a2[4] = "abc"...

The C language has three mandatory real floating point types, float, double, and long double. float f = 0.314f; /* suffix f or F denotes type float */ double d = 0.314; /* no suffix denotes double */ long double ld = 0.314l; /* suffix l or L denotes long double */ /* the differen...

Dictionaries are an unordered collection of keys and values. Values relate to unique keys and must be of the same type. When initializing a Dictionary the full syntax is as follows: var books : Dictionary<Int, String> = Dictionary<Int, String>() Although a more concise way of initia...

Add a key and value to a Dictionary var books = [Int: String]() //books = [:] books[5] = "Book 5" //books = [5: "Book 5"] books.updateValue("Book 6", forKey: 5) //[5: "Book 6"] updateValue returns the original value if one exists or nil. let previous...

A value in a Dictionary can be accessed using its key: var books: [Int: String] = [1: "Book 1", 2: "Book 2"] let bookName = books[1] //bookName = "Book 1" The values of a dictionary can be iterated through using the values property: for book in books.values { ...

The <article> element contains self-contained content like articles, blog posts, user comments or an interactive widget that could be distributed outside the context of the page, for example by RSS. When article elements are nested, the contents of the inner article node should be related t...

The <main> element contains the main content for your web page. This content is unique to the individual page, and should not appear elsewhere on the site. Repeating content like headers, footers, navigation, logos, etc., is placed outside the element. The <main> element should only e...

Syntax : history.replaceState(data, title [, url ]) This method modifies the current history entry instead of creating a new one. Mainly used when we want to update URL of the current history entry. window.history.replaceState("http://example.ca", "Sample Title", "/exam...

Syntax : history.pushState(state object, title, url) This method allows to ADD histories entries. For more reference, Please have a look on this document : pushState() method Example : window.history.pushState("http://example.ca", "Sample Title", "/example/path.html&qu...

@media screen and (min-width: 720px) { body { background-color: skyblue; } } The above media query specifies two conditions: The page must be viewed on a normal screen (not a printed page, projector, etc). The width of the user's view port must be at least 720 pixels. I...

Swift label.textAlignment = NSTextAlignment.left //or the shorter label.textAlignment = .left Any value in the NSTextAlignment enum is valid: .left, .center, .right, .justified, .natural Objective-C label.textAlignment = NSTextAlignmentLeft; Any value in the NSTextAlignment enum is vali...

With a Frame When you know the exact dimensions you want to set for your label, you can initialize a UILabel with a CGRect frame. Swift let frame = CGRect(x: 0, y: 0, width: 200, height: 21) let label = UILabel(frame: frame) view.addSubview(label) Objective-C CGRect frame = CGRectMake(0, 0,...

Use new Date() to generate a new Date object containing the current date and time. Note that Date() called without arguments is equivalent to new Date(Date.now()). Once you have a date object, you can apply any of the several available methods to extract its properties (e.g. getFullYear() to get t...

Magic (also called dunder as an abbreviation for double-underscore) methods in Python serve a similar purpose to operator overloading in other languages. They allow a class to define its behavior when it is used as an operand in unary or binary operator expressions. They also serve as implementation...

It is possible to emulate container types, which support accessing values by key or index. Consider this naive implementation of a sparse list, which stores only its non-zero elements to conserve memory. class sparselist(object): def __init__(self, size): self.size = size se...

class adder(object): def __init__(self, first): self.first = first # a(...) def __call__(self, second): return self.first + second add2 = adder(2) add2(1) # 3 add2(2) # 4