Added $modify query operator

Author: Dekel Barzilay

README.md

@@ -157,7 +157,8 @@ Note that all this eager related options are optional.
 
 #### Query Operators
 
-- **`$modify`** - modifiers allow you to easily reuse snippets of query logic. See
+- **`$modify`** - modifiers allow you to easily reuse snippets of query logic. you can pass arguments and use 
+  multiple modifiers. value can be array, a serialized JSON array or a string with modifiers separated by `,`. See
   [`modify`](https://vincit.github.io/objection.js/api/query-builder/other-methods.html#modify) documentation.
 
 - **`$eager`** - eager load relations defined in models' `relationMappings` getter methods. See

src/index.js

@@ -305,7 +305,11 @@ class Service extends AdapterService {
     }
 
     if (query && query.$modify) {
-      q.modify(...query.$modify);
+      if (typeof query.$modify === 'string') {
+        if (query.$modify[0] === '[' && query.$modify[query.$modify.length - 1] === ']') { q.modify(...JSON.parse(query.$modify)); } else { q.modify(query.$modify.split(',')); }
+      } else {
+        q.modify(...query.$modify);
+      }
 
       delete query.$modify;
     }

test/index.test.js

@@ -1690,6 +1690,27 @@ describe('Feathers Objection Service', () => {
       });
     });
 
+    it('allow $modify query as string', () => {
+      return companies.find({ query: { $modify: 'google' } }).then(data => {
+        expect(data.length).to.be.equal(1);
+        expect(data[0].name).to.be.equal('Google');
+      });
+    });
+
+    it('allow $modify query as string with multiple modifiers', () => {
+      return companies.find({ query: { $modify: 'apple,large' } }).then(data => {
+        expect(data.length).to.be.equal(1);
+        expect(data[0].name).to.be.equal('Apple');
+      });
+    });
+
+    it('allow $modify query as string array', () => {
+      return companies.find({ query: { $modify: JSON.stringify(['google']) } }).then(data => {
+        expect(data.length).to.be.equal(1);
+        expect(data[0].name).to.be.equal('Google');
+      });
+    });
+
     it('allow $modify query with args', () => {
       return companies.find({ query: { $modify: ['large', false] } }).then(data => {
         expect(data.length).to.be.equal(1);