added missing DataSnapshot methods - child, exists, getPriority, hasChild, hasChildren, numChildren

Author: Salakar

lib/modules/database/snapshot.js

@@ -2,47 +2,80 @@
  * @flow
  */
 import Reference from './reference.js';
+import { isObject, deepGet } from './../../utils';
 
 export default class Snapshot {
   static key: String;
   static value: Object;
   static exists: boolean;
   static hasChildren: boolean;
-  static childrenCount: Number;
   static childKeys: String[];
 
   ref: Object;
   key: string;
   value: any;
   exists: boolean;
   priority: any;
-  hasChildren: boolean;
-  childrenCount: number;
   childKeys: Array<string>;
 
   constructor(ref: Reference, snapshot: Object) {
     this.ref = ref;
     this.key = snapshot.key;
     this.value = snapshot.value;
     this.exists = snapshot.exists || true;
-    this.priority = snapshot.priority;
-    this.hasChildren = snapshot.hasChildren || false;
-    this.childrenCount = snapshot.childrenCount || 0;
+    this.priority = snapshot.priority === undefined ? null : snapshot.priority;
     this.childKeys = snapshot.childKeys || [];
   }
+  /*
+   * DEFAULT API METHODS
+   */
 
   val() {
     return this.value;
   }
 
+  child(path: string) {
+    const value = deepGet(this.value, path);
+    const childRef = this.ref.child(path);
+    return new Snapshot(childRef, {
+      value,
+      key: childRef.key,
+      exists: value !== null,
+      childKeys: isObject(value) ? Object.keys(value) : [],
+    });
+  }
+
+  exists() {
+    return this.value !== null;
+  }
+
   forEach(fn: (key: any) => any) {
-    (this.childKeys || [])
-      .forEach(key => fn(this.value[key]));
+    (this.childKeys || []).forEach((key, i) => fn(this.value[key], i));
+  }
+
+  getPriority() {
+    return this.priority;
+  }
+
+  hasChild(key: string) {
+    return this.childKeys.includes(key);
+  }
+
+  hasChildren() {
+    return this.numChildren() > 0;
+  }
+
+  numChildren() {
+    if (!isObject(this.value)) return 0;
+    return Object.keys(this.value).length;
   }
 
+  /*
+   * EXTRA API METHODS
+   */
   map(fn: (key: string) => mixed) {
     const arr = [];
-    this.forEach(item => arr.push(fn(item)));
+    this.forEach((item, i) => arr.push(fn(item, i)));
     return arr;
   }