fix(dcmjs): Add a set of accessors to the sequence list so the API is…

… more consistent (dcmjs-org#224)

* fix(dcmjs): Add a set of accessors to the sequence list so the API is more consistent.

* fix(dcmjs): Added documentation on the addAccessors as requested

src/DicomMetaDictionary.js

@@ -1,6 +1,7 @@
 import log from "./log.js";
-import { ValueRepresentation } from "./ValueRepresentation.js";
-import dictionary from "./dictionary.js";
+import { ValueRepresentation } from "./ValueRepresentation";
+import dictionary from "./dictionary";
+import addAccessors from "./utilities/addAccessors";
 
 class DicomMetaDictionary {
     // intakes a custom dictionary that will be used to parse/denaturalize the dataset
@@ -85,11 +86,13 @@ class DicomMetaDictionary {
         return namedDataset;
     }
 
-    // converts from DICOM JSON Model dataset
-    // to a natural dataset
-    // - sequences become lists
-    // - single element lists are replaced by their first element
-    // - object member names are dictionary, not group/element tag
+    /** converts from DICOM JSON Model dataset to a natural dataset
+     * - sequences become lists
+     * - single element lists are replaced by their first element,
+     *     with single element lists remaining lists, but being a
+     *     proxy for the child values, see addAccessors for examples
+     * - object member names are dictionary, not group/element tag
+     */
     static naturalizeDataset(dataset) {
         const naturalDataset = {
             _vrMap: {}
@@ -142,8 +145,16 @@ class DicomMetaDictionary {
                 }
 
                 if (naturalDataset[naturalName].length === 1) {
-                    naturalDataset[naturalName] =
-                        naturalDataset[naturalName][0];
+                    const sqZero = naturalDataset[naturalName][0];
+                    if (
+                        sqZero &&
+                        typeof sqZero === "object" &&
+                        !sqZero.length
+                    ) {
+                        addAccessors(naturalDataset[naturalName], sqZero);
+                    } else {
+                        naturalDataset[naturalName] = sqZero;
+                    }
                 }
             }
         });

src/utilities/addAccessors.js

@@ -0,0 +1,26 @@
+/**
+ * Adds accessors (set/get) to dest for every property in src.
+ * @example
+ * src = [{a:5,b:'string', c:null}]
+ * addAccessors(src)
+ * src.c = 'outerChange'
+ * src[0].b='innerChange'
+ *
+ * assert src.a===5
+ * assert src[0].c === 'outerChange'
+ * assert src.b === 'innerChange'
+ */
+const addAccessors = (dest, src) => {
+    Object.keys(src).forEach(key => {
+        Object.defineProperty(dest, key, {
+            get: () => {
+                return src[key];
+            },
+            set: v => {
+                src[key] = v;
+            }
+        });
+    });
+};
+
+export default addAccessors;

src/utilities/index.js

@@ -1,11 +1,13 @@
 import TID1500 from "./TID1500/index.js";
 import TID300 from "./TID300/index.js";
 import message from "./Message.js";
+import addAccessors from "./addAccessors.js";
 
 const utilities = {
     TID1500,
     TID300,
-    message
+    message,
+    addAccessors
 };
 
 export default utilities;

test/test_data.js

@@ -165,7 +165,8 @@ const tests = {
         const spacing = naturalSequence.SharedFunctionalGroupsSequence
             .PixelMeasuresSequence.SpacingBetweenSlices;
         expect(spacing).to.equal(0.12);
-
+        expect(Array.isArray(naturalSequence.SharedFunctionalGroupsSequence)).to.equal(true);
+
         expect(naturalSequence.ProcedureCodeSequence).to.have.property(
             "CodingSchemeDesignator",
             "L"

test/test_utilities.js

@@ -1,5 +1,30 @@
+const expect = require("chai").expect;
+const dcmjs = require("../build/dcmjs");
+const { utilities } = dcmjs;
+const { addAccessors } = utilities;
 
 exports.test = () => {
-  console.log('no tests yet');
+  const tests = {
+    testAddAccessor: () => {
+      const baseValue = { a: 1, b: 2 };
+      const arrValue = [baseValue];
+      addAccessors(arrValue, baseValue);
+      expect(arrValue.a).to.equal(1);
+      baseValue.a = 3;
+      expect(arrValue.a).to.equal(3);
+      arrValue.b = 4;
+      expect(baseValue.b).to.equal(4);
+      const forArr = [];
+      arrValue.forEach(item => forArr.push(item));
+      expect(forArr.length).to.equal(1);
+    },
+  };
+
+  Object.keys(tests).forEach(testKey => {
+    console.log('Running', testKey);
+    const test = tests[testKey];
+    test();
+    console.log('Done running', testKey);
+  });
 }