[General] Added collection shortcuts for Observable.

RxShortcuts/RxSwift/Collection+Shortcuts.swift

@@ -0,0 +1,58 @@
+//
+//  Collection+Shortcuts.swift
+//  RxShortcuts
+//
+//  Created by sunshinejr on 25.11.2016.
+//  Copyright (c) 2016 sunshinejr. All rights reserved.
+//
+
+import RxSwift
+
+public extension Collection where Iterator.Element: ObservableType {
+
+    /**
+     Merges elements from all observable sequences in the given enumerable sequence into a single observable sequence.
+     
+     - seealso: [merge operator on reactivex.io](http://reactivex.io/documentation/operators/merge.html)
+     
+     - returns: The observable sequence that merges the elements of the observable sequences.
+     */
+    func merge() -> Observable<Self.Iterator.Element.E> {
+        return Observable.from(self).merge()
+    }
+
+    /**
+     Merges the specified observable sequences into one observable sequence by using the selector function whenever any of the observable sequences produces an element.
+     
+     - seealso: [combineLatest operator on reactivex.io](http://reactivex.io/documentation/operators/combinelatest.html)
+     
+     - parameter resultSelector: Function to invoke whenever any of the sources produces an element.
+     - returns: An observable sequence containing the result of combining elements of the sources using the specified result selector function.
+     */    
+    func combineLatest<T>(resultSelector: @escaping ([Self.Iterator.Element.E]) throws -> T) -> Observable<T> {
+        return Observable.combineLatest(self, resultSelector)
+    }
+
+    /**
+     Merges the specified observable sequences into one observable sequence by using the selector function whenever all of the observable sequences have produced an element at a corresponding index.
+     
+     - seealso: [zip operator on reactivex.io](http://reactivex.io/documentation/operators/zip.html)
+     
+     - parameter resultSelector: Function to invoke for each series of elements at corresponding indexes in the sources.
+     - returns: An observable sequence containing the result of combining elements of the sources using the specified result selector function.
+     */
+    func zip<T>(resultSelector: @escaping ([Self.Iterator.Element.E]) throws -> T) -> Observable<T> {
+        return Observable.zip(self, resultSelector)
+    }
+
+    /**
+     Concatenates all inner observable sequences, as long as the previous observable sequence terminated successfully.
+     
+     - seealso: [concat operator on reactivex.io](http://reactivex.io/documentation/operators/concat.html)
+     
+     - returns: An observable sequence that contains the elements of each observed inner sequence, in sequential order.
+     */
+    func concat() -> Observable<Self.Iterator.Element.E> {
+        return Observable.from(self).concat()
+    }
+}