Add methods to render an array of nodes

Stencil/Node.swift

@@ -16,6 +16,37 @@ public protocol Node {
     func render(context:Context) -> (String?, Error?)
 }
 
+extension Array {
+    func map<U>(block:((Element) -> (U?, Error?))) -> ([U]?, Error?) {
+        var results = [U]()
+
+        for item in self {
+            let (result, error) = block(item)
+
+            if let error = error {
+                return (nil, error)
+            } else if (result != nil) {
+                // let result = result exposing a bug in the Swift compier :(
+                results.append(result!)
+            }
+        }
+
+        return (results, nil)
+    }
+}
+
+public func render(nodes:[Node], context:Context) -> (String?, Error?) {
+    let result:(results:[String]?, error:Error?) = nodes.map {
+        return $0.render(context)
+    }
+
+    if let result = result.0 {
+        return ("".join(result), nil)
+    }
+
+    return (nil, result.1)
+}
+
 public class TextNode : Node {
     public let text:String
 

StencilTests/NodeTests.swift

@@ -10,6 +10,19 @@ import Cocoa
 import XCTest
 import Stencil
 
+class ErrorNodeError : Error {
+    var description: String {
+        return "Node Error"
+    }
+}
+
+class ErrorNode : Node {
+    func render(context: Context) -> (String?, Error?) {
+
+        return (nil, ErrorNodeError())
+    }
+}
+
 class NodeTests: XCTestCase {
     var context:Context!
 
@@ -45,3 +58,21 @@ class VariableNodeTests: NodeTests {
         XCTAssertEqual(result.0!, "27")
     }
 }
+
+class RenderNodeTests: NodeTests {
+    func testRenderingNodes() {
+        let nodes = [TextNode(text:"Hello "), VariableNode(variable: "name")] as [Node]
+        let (result:String?, error:Error?) = render(nodes, context)
+
+        XCTAssertEqual(result!, "Hello Kyle")
+        XCTAssertTrue(error == nil)
+    }
+
+    func testRenderingNodesWithFailure() {
+        let nodes = [TextNode(text:"Hello "), VariableNode(variable: "name"), ErrorNode()] as [Node]
+        let (result:String?, error:Error?) = render(nodes, context)
+
+        XCTAssertEqual(error!.description, "Node Error")
+        XCTAssertTrue(result == nil)
+    }
+}