mapping: array field should return empty array rather than error when…

… the field is missing

spec/example/facebook_adcreatives_spec.cr

@@ -0,0 +1,74 @@
+require "./spec_helper"
+
+module Example::Facebook::AdCreatives
+  # account.adcreatives(fields: %w( title object_story_id object_story_spec ))
+  STR = <<-EOF
+  [
+    {
+      "title": "abc",
+      "object_story_spec": {
+        "page_id": "012345...",
+        "link_data": {
+          "link": "http://example.com/",
+          "message": "advertise message",
+          "name": "title",
+          "attachment_style": "link",
+          "image_hash": "c9e4c9...",
+          "call_to_action": {
+            "type": "LEARN_MORE"
+          },
+          "child_attachments": [
+            {
+              "link": "http://example.com/1",
+              "image_hash": "405bf...",
+              "name": "title of carousel1",
+              "call_to_action": {
+                "type": "LEARN_MORE"
+              }
+            },
+            {
+              "link": "http://example.com/2",
+              "image_hash": "9cef4...",
+              "name": "title of carousel2",
+              "call_to_action": {
+                "type": "LEARN_MORE"
+              }
+            }
+          ]
+        }
+      }
+    }
+  ]
+  EOF
+
+  class Attachment
+    Jq.mapping({
+      link:        String,
+      name:        String,
+    })
+  end
+
+  class LinkData
+    Jq.mapping({
+      link:        String,
+      message:     String,
+      name:        String,
+      attachments: {Array(Attachment), ".child_attachments"},
+    })
+  end
+
+  class AdCreative
+    Jq.mapping({
+      title:     String,
+      link_data: {LinkData, ".object_story_spec.link_data"},
+    })
+  end
+
+  describe "Example::Facebook::AdCreatives" do
+    it "works" do
+      creatives = Array(AdCreative).from_json(STR)
+      link = creatives[0].link_data
+      link.attachments.map(&.link).should eq(["http://example.com/1","http://example.com/2"])
+    end
+  end
+end

spec/example/facebook_adimages_spec.cr

@@ -0,0 +1,38 @@
+require "./spec_helper"
+
+module Example::Facebook::AdImages
+  # account.adimages(fields: ["name", "status", "creatives"])
+  STR = <<-EOF
+  [
+    {
+      "name": "abc",
+      "status": "ACTIVE",
+      "creatives": ["123456","789012"]
+    },
+    {
+      "name": "xyz",
+      "status": "ACTIVE"
+    }
+  ]
+  EOF
+
+  class AdImage
+    Jq.mapping({
+      name:      String,
+      status:    String,
+      creatives: {Array(String), ".creatives"}
+    })
+  end
+
+  describe "Example::Facebook::AdImages" do
+    it "works with array field" do
+      images = Array(AdImage).from_json(STR)
+      images[0].creatives.should eq(["123456","789012"])
+    end
+
+    it "return empty array when array field is missing" do
+      images = Array(AdImage).from_json(STR)
+      images[1].creatives.should eq(Array(String).new)
+    end
+  end
+end

src/jq/mapping.cr

@@ -34,7 +34,11 @@ class Jq
 
       def {{key.id}}
         if @{{key.id}}.nil?
-          default_{{key.id}}
+          {% if tuple[0].stringify =~ /^Array\(/ %}
+            {{tuple[0]}}.new
+          {% else %}
+            default_{{key.id}}
+          {% end %}
         else
           @{{key.id}}.not_nil!
         end