add my swift style ideas

Author: jqsilver

swift.md

@@ -2,3 +2,198 @@
 
 *Swift*
 
+# Swift Style Guide
+
+* capitalize constants, and prefer putting them in the top level of a class if they are private. If they are public, put the constant as a static property, so we get nice namespaces.  
+```swift
+private let PrivateValue = "secret"
+  
+class MyClass {
+  static let PublicValue = "something"
+
+  func doSomething() {
+    print(MaxTime)
+  }
+}
+```
+    
+* always use “self” for properties. Don’t use it for methods. 
+```swift
+class MyClass {
+  var aProp: Int
+    
+  func doSomething() {
+    // WRONG
+    aProp = 4
+    
+    // RIGHT
+    self.aProp = 4
+    
+    // WRONG
+    self.otherMethod()
+    
+    // RIGHT
+    otherMethod()
+  }
+}
+```    
+
+* Try to initialize properties in the init() method whenever possible, rather than using implicitly unwrapped optionals.  (Notable exception is UIViewController.)
+```swift
+// WRONG
+class MyClass: NSObject {
+  var someValue: Int!
+  init() {
+    super.init()
+    someValue = 5
+  }
+}
+
+// RIGHT
+class MyClass: NSObject {
+  var someValue: Int
+  init() {
+    someValue = 0
+    super.init()
+  }
+}
+```
+
+* Use functions instead of computed properties if they get to be complicated. Also avoid didSet and willSet for the same reason. 
+```swift
+// WRONG
+// this is less readable
+class MyClass {
+  var someValue: Int {
+    get {
+      // return something computed
+    }
+    set(newValue) {
+      // set a bunch of other values
+    }
+  }
+}
+
+// RIGHT
+// easier to read more clear that there are side effects of setting
+class MyClass {
+  func someValue() {
+  }
+  
+  func setSomeValue() {
+  }
+}
+```
+* Separate long function names on each argument and put the open curly on the next line so the body is indented correctly. 
+```swift
+class MyClass {
+  // WRONG
+  func doSomething(arg: Int, anotherArg: Int, yetAnotherArg: Int, andOneMoreArgForGoodMeasure: String) {
+      // This is just too long and will probably auto-wrap in a weird way
+  }
+  
+  // WRONG
+  func doSomething(arg: Int,
+    anotherArg: Int,
+    yetAnotherArg: Int,
+    andOneMoreArgForGoodMeasure: String) {
+      // XCode will indent the body an extra level in
+  }
+  
+  func doSomething(
+    arg: Int,
+    anotherArg: Int,
+    yetAnotherArg: Int,
+    andOneMoreArgForGoodMeasure: String) 
+  {
+    // Will cause correct level of indentation
+  }
+}
+```
+    
+* Avoid large callback blocks - instead organize them into methods.  This makes weak-self in blocks much simpler.
+```swift
+    // WRONG
+    class MyClass {
+      func doRequest(completion: () -> Void) {
+        API.request() { response in
+          // lots of processing and whatever
+          completion()
+        }
+      }
+    }
+    
+    // RIGHT
+    class MyClass {
+      func doRequest(completion: () -> Void) {
+        API.request() { response in 
+          self.processResponse(response)
+          completion()
+        }
+      }
+      
+      func processResponse(response) {
+        // do actual processing here
+      }
+    }
+```
+      
+* Guard
+    * Only add to top of functions. Goal of guard is to reduce branch complexity and in some ways adding guard statements in the middle of a chunk of code increases complexity
+
+* How do we deal with multiple let clauses in an if clause?
+```swift
+    // This feels weird, but is how autoindent works right now in XCode
+    if
+      let val1 = val1,
+      let val2 = val2
+      where !val2.isEmpty {
+      print(val2)
+    }
+    
+    // Putting the first let on the same line as the if makes the body indent an extra level
+    // This also looks kind of gross
+    if let val1 = val1,
+      let val2 = val2
+      where !val2.isEmpty {
+        print(val2)
+    }
+```
+* Don’t include return type Void in blocks even though that’s what autocomplete does
+```swift
+	// WRONG
+    someAsyncThing() { argument -> Void in ... }
+    
+    // RIGHT
+    someAsyncThing() { argument in ... }
+```
+
+* prefer immutable values whenever possible. use map and flatmap instead of appending to a new array.  mutable variables increase complexity, so try to keep them in as small a scope as possible if you have to use them. 
+```swift
+	// WRONG
+    var results = []
+    for element in input {
+      let result = transform(element)
+      results.append(result)
+    }
+    
+    // RIGHT
+    let results = input.map(transform)
+    
+    // WRONG
+    func doSomething() {
+      var someHash = getHashFromSomewhere()
+      someHash["someNewKey"] = someComputation()
+      doSomethingWithHash(someHash)
+    }
+    
+    // RIGHT 
+    func doSomething() {
+      let someHash = getHashFromSomewhere()
+      let modifiedHash = modifyHash(someHash)
+      doSomethingWithHash(modifiedHash)
+    }
+```
+* Avoid using optionals unless there’s a good semantic meaning.
+
+