R/iosdev: A subreddit focused on iOS development. I'd mostly worry about fan noise, with the MacBook Air. So I'd go with recommending the slowest dual core i3 variant, since it's closer the low thermal radiator capacity of the chassis. Created To Make You Think: Meet Our New Printed Magazine Created To Make You Think: Meet Our New Printed Magazine Vitaly Friedman 2019-07-24T08:02:02+-07-24T12:35:56+00:00.
For Swift 5, Xcode 11.3 & Catalina Support and updated README, please check the 'swift5' branch. Thanks revblaze's conribution. Google Analytics for Mac OS X using Swift. As we know, Google Analytics is perfect for user data collection and analytics. But unfortunately, there's no official SDK for Mac OS X. Sep 19, 2018 Open Xcode and create a new iOS project based on the Single View App template. Name the app HitList and make sure Use Core Data is checked. Checking the Use Core Data box will cause Xcode to generate boilerplate code for what’s known as an NSPersistentContainer in AppDelegate.swift. Apr 19, 2017 Open Xcode and click Get started with a playground in the Welcome to Xcode window, or choose File/New/Playground Set the name of the playground to Files, make sure the Platform is set to macOS and click Next. Select your Desktop and click Create to save the playground.
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Swift provides three primary collection types, known as arrays, sets, and dictionaries, for storing collections of values. Arrays are ordered collections of values. Sets are unordered collections of unique values. Dictionaries are unordered collections of key-value associations.
Arrays, sets, and dictionaries in Swift are always clear about the types of values and keys that they can store. This means that you cannot insert a value of the wrong type into a collection by mistake. It also means you can be confident about the type of values you will retrieve from a collection.
Note
Swift’s array, set, and dictionary types are implemented as generic collections. For more about generic types and collections, see Generics.
Mutability of Collections¶
If you create an array, a set, or a dictionary, and assign it to a variable, the collection that is created will be mutable. This means that you can change (or mutate) the collection after it’s created by adding, removing, or changing items in the collection. If you assign an array, a set, or a dictionary to a constant, that collection is immutable, and its size and contents cannot be changed.
Note
It is good practice to create immutable collections in all cases where the collection does not need to change. Doing so makes it easier for you to reason about your code and enables the Swift compiler to optimize the performance of the collections you create.
Arrays¶
An array stores values of the same type in an ordered list. The same value can appear in an array multiple times at different positions.
Note
Swift’s
Array type is bridged to Foundation’s NSArray class.
For more information about using
Array with Foundation and Cocoa, see Bridging Between Array and NSArray.
Array Type Shorthand Syntax¶
The type of a Swift array is written in full as
Array<Element> , where Element is the type of values the array is allowed to store. You can also write the type of an array in shorthand form as [Element] . Although the two forms are functionally identical, the shorthand form is preferred and is used throughout this guide when referring to the type of an array.
Creating an Empty Array¶
You can create an empty array of a certain type using initializer syntax:
Note that the type of the
someInts variable is inferred to be [Int] from the type of the initializer.
Alternatively, if the context already provides type information, such as a function argument or an already typed variable or constant, you can create an empty array with an empty array literal, which is written as
[] (an empty pair of square brackets):
Creating an Array with a Default Value¶
Swift’s
Array type also provides an initializer for creating an array of a certain size with all of its values set to the same default value. You pass this initializer a default value of the appropriate type (called repeating ): and the number of times that value is repeated in the new array (called count ):
Creating an Array by Adding Two Arrays Together¶
You can create a new array by adding together two existing arrays with compatible types with the addition operator (
+ ). The new array’s type is inferred from the type of the two arrays you add together:
Creating an Array with an Array Literal¶
You can also initialize an array with an array literal, which is a shorthand way to write one or more values as an array collection. An array literal is written as a list of values, separated by commas, surrounded by a pair of square brackets:
The example below creates an array called
shoppingList to store String values:
The
shoppingList variable is declared as “an array of string values”, written as [String] . Because this particular array has specified a value type of String , it is allowed to store String values only. Here, the shoppingList array is initialized with two String values ('Eggs' and 'Milk' ), written within an array literal.
Note
The
shoppingList array is declared as a variable (with the var introducer) and not a constant (with the let introducer) because more items are added to the shopping list in the examples below.
In this case, the array literal contains two
String values and nothing else. This matches the type of the shoppingList variable’s declaration (an array that can only contain String values), and so the assignment of the array literal is permitted as a way to initialize shoppingList with two initial items.
Thanks to Swift’s type inference, you don’t have to write the type of the array if you’re initializing it with an array literal containing values of the same type. The initialization of
shoppingList could have been written in a shorter form instead:
Because all values in the array literal are of the same type, Swift can infer that
[String] is the correct type to use for the shoppingList variable.
Accessing and Modifying an Array¶
You access and modify an array through its methods and properties, or by using subscript syntax.
To find out the number of items in an array, check its read-only
count property:
Use the Boolean
isEmpty property as a shortcut for checking whether the count property is equal to 0 :
You can add a new item to the end of an array by calling the array’s
append(_:) method:
Alternatively, append an array of one or more compatible items with the addition assignment operator (
+= ):
Retrieve a value from the array by using subscript syntax, passing the index of the value you want to retrieve within square brackets immediately after the name of the array:
Note
The first item in the array has an index of
0 , not 1 . Arrays in Swift are always zero-indexed.
You can use subscript syntax to change an existing value at a given index:
When you use subscript syntax, the index you specify needs to be valid. For example, writing
shoppingList[shoppingList.count]='Salt' to try to append an item to the end of the array results in a runtime error.
You can also use subscript syntax to change a range of values at once, even if the replacement set of values has a different length than the range you are replacing. The following example replaces
'ChocolateSpread' , 'Cheese' , and 'Butter' with 'Bananas' and 'Apples' :
To insert an item into the array at a specified index, call the array’s
insert(_:at:) method:
This call to the
insert(_:at:) method inserts a new item with a value of 'MapleSyrup' at the very beginning of the shopping list, indicated by an index of 0 .
Similarly, you remove an item from the array with the
remove(at:) method. This method removes the item at the specified index and returns the removed item (although you can ignore the returned value if you do not need it):
Note
If you try to access or modify a value for an index that is outside of an array’s existing bounds, you will trigger a runtime error. You can check that an index is valid before using it by comparing it to the array’s
count property. The largest valid index in an array is count-1 because arrays are indexed from zero—however, when count is 0 (meaning the array is empty), there are no valid indexes.
Any gaps in an array are closed when an item is removed, and so the value at index
0 is once again equal to 'Sixeggs' :
If you want to remove the final item from an array, use the
removeLast() method rather than the remove(at:) method to avoid the need to query the array’s count property. Like the remove(at:) method, removeLast() returns the removed item:
Iterating Over an Array¶
You can iterate over the entire set of values in an array with the
for -in loop:
If you need the integer index of each item as well as its value, use the
enumerated() method to iterate over the array instead. For each item in the array, the enumerated() method returns a tuple composed of an integer and the item. The integers start at zero and count up by one for each item; if you enumerate over a whole array, these integers match the items’ indices. You can decompose the tuple into temporary constants or variables as part of the iteration:
For more about the
for -in loop, see For-In Loops.
Sets¶
A set stores distinct values of the same type in a collection with no defined ordering. You can use a set instead of an array when the order of items is not important, or when you need to ensure that an item only appears once.
Note
Swift’s
Set type is bridged to Foundation’s NSSet class.
For more information about using
Set with Foundation and Cocoa, see Bridging Between Set and NSSet.
Hash Values for Set Types¶
A type must be hashable in order to be stored in a set—that is, the type must provide a way to compute a hash value for itself. A hash value is an
Int value that is the same for all objects that compare equally, such that if ab , it follows that a.hashValueb.hashValue .
All of Swift’s basic types (such as
String , Int , Double , and Bool ) are hashable by default, and can be used as set value types or dictionary key types. Enumeration case values without associated values (as described in Enumerations) are also hashable by default.
Note
You can use your own custom types as set value types or dictionary key types by making them conform to the
Hashable protocol from Swift’s standard library. Types that conform to the Hashable protocol must provide a gettable Int property called hashValue . The value returned by a type’s hashValue property is not required to be the same across different executions of the same program, or in different programs.
Because the
Hashable protocol conforms to Equatable , conforming types must also provide an implementation of the equals operator (). The Equatable protocol requires any conforming implementation of to be an equivalence relation. That is, an implementation of must satisfy the following three conditions, for all values a , b , and c :
For more information about conforming to protocols, see Protocols.
Set Type Syntax¶
The type of a Swift set is written as
Set<Element> , where Element is the type that the set is allowed to store. Unlike arrays, sets do not have an equivalent shorthand form.
Creating and Initializing an Empty Set¶
You can create an empty set of a certain type using initializer syntax:
Note
The type of the
letters variable is inferred to be Set<Character> , from the type of the initializer.
Alternatively, if the context already provides type information, such as a function argument or an already typed variable or constant, you can create an empty set with an empty array literal:
Creating a Set with an Array Literal¶
You can also initialize a set with an array literal, as a shorthand way to write one or more values as a set collection.
The example below creates a set called
favoriteGenres to store String values:
The
favoriteGenres variable is declared as “a set of String values”, written as Set<String> . Because this particular set has specified a value type of String , it is only allowed to store String values. Here, the favoriteGenres set is initialized with three String values ('Rock' , 'Classical' , and 'Hiphop' ), written within an array literal.
Note
The
favoriteGenres set is declared as a variable (with the var introducer) and not a constant (with the let introducer) because items are added and removed in the examples below.
A set type cannot be inferred from an array literal alone, so the type
Set must be explicitly declared. However, because of Swift’s type inference, you don’t have to write the type of the set’s elements if you’re initializing it with an array literal that contains values of just one type. The initialization of favoriteGenres could have been written in a shorter form instead:
Because all values in the array literal are of the same type, Swift can infer that
Set<String> is the correct type to use for the favoriteGenres variable.
Accessing and Modifying a Set¶
You access and modify a set through its methods and properties.
To find out the number of items in a set, check its read-only
count property:
Use the Boolean
isEmpty property as a shortcut for checking whether the count property is equal to 0 :
You can add a new item into a set by calling the set’s
insert(_:) method:
You can remove an item from a set by calling the set’s
remove(_:) method, which removes the item if it’s a member of the set, and returns the removed value, or returns nil if the set did not contain it. Alternatively, all items in a set can be removed with its removeAll() method.
To check whether a set contains a particular item, use the
contains(_:) method.
Iterating Over a Set¶
You can iterate over the values in a set with a
for -in loop.
For more about the
for -in loop, see For-In Loops.
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Swift’s
Set type does not have a defined ordering. To iterate over the values of a set in a specific order, use the sorted() method, which returns the set’s elements as an array sorted using the < operator.
Performing Set Operations¶
You can efficiently perform fundamental set operations, such as combining two sets together, determining which values two sets have in common, or determining whether two sets contain all, some, or none of the same values.
Fundamental Set Operations¶
The illustration below depicts two sets--
a and b —with the results of various set operations represented by the shaded regions.
Set Membership and Equality¶
The illustration below depicts three sets--
a , b and c —with overlapping regions representing elements shared among sets. Set a is a superset of set b , because a contains all elements in b . Conversely, set b is a subset of set a , because all elements in b are also contained by a . Set b and set c are disjoint with one another, because they share no elements in common.
Xcode Macos Swift Nspanel For Data Collection 2017Dictionaries¶
A dictionary stores associations between keys of the same type and values of the same type in a collection with no defined ordering. Each value is associated with a unique key, which acts as an identifier for that value within the dictionary. Unlike items in an array, items in a dictionary do not have a specified order. You use a dictionary when you need to look up values based on their identifier, in much the same way that a real-world dictionary is used to look up the definition for a particular word.
Note
Swift’s
Dictionary type is bridged to Foundation’s NSDictionary class.
For more information about using
Dictionary with Foundation and Cocoa, see Bridging Between Dictionary and NSDictionary.
Dictionary Type Shorthand Syntax¶
The type of a Swift dictionary is written in full as
Dictionary<Key,Value> , where Key is the type of value that can be used as a dictionary key, and Value is the type of value that the dictionary stores for those keys.
Note
A dictionary
Key type must conform to the Hashable protocol, like a set’s value type.
You can also write the type of a dictionary in shorthand form as
[Key:Value] . Although the two forms are functionally identical, the shorthand form is preferred and is used throughout this guide when referring to the type of a dictionary.
Creating an Empty Dictionary¶
As with arrays, you can create an empty
Dictionary of a certain type by using initializer syntax:
This example creates an empty dictionary of type
[Int:String] to store human-readable names of integer values. Its keys are of type Int , and its values are of type String .
If the context already provides type information, you can create an empty dictionary with an empty dictionary literal, which is written as
[:] (a colon inside a pair of square brackets):
Creating a Dictionary with a Dictionary Literal¶
You can also initialize a dictionary with a dictionary literal, which has a similar syntax to the array literal seen earlier. A dictionary literal is a shorthand way to write one or more key-value pairs as a
Dictionary collection.
A key-value pair is a combination of a key and a value. In a dictionary literal, the key and value in each key-value pair are separated by a colon. The key-value pairs are written as a list, separated by commas, surrounded by a pair of square brackets:
The example below creates a dictionary to store the names of international airports. In this dictionary, the keys are three-letter International Air Transport Association codes, and the values are airport names:
The
airports dictionary is declared as having a type of [String:String] , which means “a Dictionary whose keys are of type String , and whose values are also of type String ”.
Note
The
airports dictionary is declared as a variable (with the var introducer), and not a constant (with the let introducer), because more airports are added to the dictionary in the examples below.
The
airports dictionary is initialized with a dictionary literal containing two key-value pairs. The first pair has a key of 'YYZ' and a value of 'TorontoPearson' . The second pair has a key of 'DUB' and a value of 'Dublin' .
Xcode Macos Swift Nspanel For Data Collection 2016
This dictionary literal contains two
String:String pairs. This key-value type matches the type of the airports variable declaration (a dictionary with only String keys, and only String values), and so the assignment of the dictionary literal is permitted as a way to initialize the airports dictionary with two initial items.
As with arrays, you don’t have to write the type of the dictionary if you’re initializing it with a dictionary literal whose keys and values have consistent types. The initialization of
airports could have been written in a shorter form instead:
Because all keys in the literal are of the same type as each other, and likewise all values are of the same type as each other, Swift can infer that
[String:String] is the correct type to use for the airports dictionary.
Accessing and Modifying a Dictionary¶
You access and modify a dictionary through its methods and properties, or by using subscript syntax.
As with an array, you find out the number of items in a
Dictionary by checking its read-only count property:
Use the Boolean
isEmpty property as a shortcut for checking whether the count property is equal to 0 :
You can add a new item to a dictionary with subscript syntax. Use a new key of the appropriate type as the subscript index, and assign a new value of the appropriate type:
You can also use subscript syntax to change the value associated with a particular key:
As an alternative to subscripting, use a dictionary’s
updateValue(_:forKey:) method to set or update the value for a particular key. Like the subscript examples above, the updateValue(_:forKey:) method sets a value for a key if none exists, or updates the value if that key already exists. Unlike a subscript, however, the updateValue(_:forKey:) method returns the old value after performing an update. This enables you to check whether or not an update took place.
Xcode Macos Swift Nspanel For Data Collection Youtube
The
updateValue(_:forKey:) method returns an optional value of the dictionary’s value type. For a dictionary that stores String values, for example, the method returns a value of type String? , or “optional String ”. This optional value contains the old value for that key if one existed before the update, or nil if no value existed:
You can also use subscript syntax to retrieve a value from the dictionary for a particular key. Because it is possible to request a key for which no value exists, a dictionary’s subscript returns an optional value of the dictionary’s value type. If the dictionary contains a value for the requested key, the subscript returns an optional value containing the existing value for that key. Otherwise, the subscript returns
nil :
You can use subscript syntax to remove a key-value pair from a dictionary by assigning a value of
nil for that key:
Alternatively, remove a key-value pair from a dictionary with the
removeValue(forKey:) method. This method removes the key-value pair if it exists and returns the removed value, or returns nil if no value existed:
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Iterating Over a Dictionary¶
You can iterate over the key-value pairs in a dictionary with a
for -in loop. Each item in the dictionary is returned as a (key,value) tuple, and you can decompose the tuple’s members into temporary constants or variables as part of the iteration:
For more about the
for -in loop, see For-In Loops.
You can also retrieve an iterable collection of a dictionary’s keys or values by accessing its
keys and values properties:
If you need to use a dictionary’s keys or values with an API that takes an
Array instance, initialize a new array with the keys or values property:
Swift’s
Dictionary type does not have a defined ordering. To iterate over the keys or values of a dictionary in a specific order, use the sorted() method on its keys or values property.
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