- only allow characteristics with value to be read only (#194)

README.md

@@ -174,7 +174,7 @@ var characteristic = new Characteristic({
     uuid: 'fffffffffffffffffffffffffffffff1', // or 'fff1' for 16-bit
     properties: [ ... ], // can be a combination of 'read', 'write', 'writeWithoutResponse', 'notify', 'indicate'
     secure: [ ... ], // enable security for properties, can be a combination of 'read', 'write', 'writeWithoutResponse', 'notify', 'indicate'
-    value: null, // optional static value, must be of type Buffer
+    value: null, // optional static value, must be of type Buffer - for read only characteristics
     descriptors: [
         // see Descriptor for data type
     ],

lib/characteristic.js

@@ -12,6 +12,10 @@ function Characteristic(options) {
   this.value = options.value || null;
   this.descriptors = options.descriptors || [];
 
+  if (this.value && (this.properties.length !== 1 || this.properties[0] !== 'read')) {
+    throw new Error('Characteristics with value can be read only!');
+  }
+
   if (options.onReadRequest) {
     this.onReadRequest = options.onReadRequest;
   }

test/test-characteristic.js

@@ -56,12 +56,22 @@ describe('Characteristic', function() {
 
   it('should create with value option', function() {
     var characteristic = new Characteristic({
+      properties: ['read'],
       value: mockValue
     });
 
     characteristic.value.should.equal(mockValue);
   });
 
+  it('should not create with value option and non-read properties', function() {
+    (function(){
+      var characteristic = new Characteristic({
+        properties: ['write'],
+        value: mockValue
+      });
+    }).should.throw();
+  });
+
   it('should create with descriptors option', function() {
     var characteristic = new Characteristic({
       descriptors: mockDescriptors