Block写法
看到一个很不错的Block写法总结，为了方便拷过来了，参考链接：http://www.jianshu.com/p/f827a15aa78f
As a local variable:
returnType (^blockName)(parameterTypes) = ^returnType(parameters) {...};
As a property:
@property (nonatomic, copy) returnType (^blockName)(parameterTypes);
As a method parameter:
- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))blockName;
As an argument to a method call:
[someObject someMethodThatTakesABlock:^returnType (parameters) {...}];
As a typedef:
typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};As a variable:
var closureName: (ParameterTypes) -> ReturnType
As a type alias:
typealias ClosureType = (ParameterTypes) -> ReturnType
As a constant:
let closureName: ClosureType = { ... }
As a parameter to another function:
funcName(parameter: (ParameterTypes) -> ReturnType)
Note: if the passed-in closure is going to outlive the scope of the method, e.g. if you are saving it to a property, it needs to be annotated with @escaping.
As an argument to a function call:
funcName({ (ParameterTypes) -> ReturnType in statements })
As a function parameter:
array.sorted(by: { (item1: Int, item2: Int) -> Bool in return item1 < item2 })
As a function parameter with implied types:
array.sorted(by: { (item1, item2) -> Bool in return item1 < item2 })
As a function parameter with implied return type:
array.sorted(by: { (item1, item2) in return item1 < item2 })
As the last function parameter:
array.sorted { (item1, item2) in return item1 < item2 }
As the last parameter, using shorthand argument names:
array.sorted { return $0 < $1 }
As the last parameter, with an implied return value:
array.sorted { $0 < $1 }
As the last parameter, as a reference to an existing function:
array.sorted(by: <)
As a function parameter with explicit capture semantics:
array.sorted(by: { [unowned self] (item1: Int, item2: Int) -> Bool in return item1 < item2 })
As a function parameter with explicit capture semantics and inferred parameters / return type:
array.sorted(by: { [unowned self] in return $0 < $1 })
