From 2ae6f0a11307ede2b634d24dc97995fd798319ac Mon Sep 17 00:00:00 2001
From: Aaron Jensen <aaronjensen@gmail.com>
Date: Tue, 4 Aug 2015 22:28:31 -0700
Subject: [PATCH] Add u.in and rework readme

---
 CHANGELOG.md        |  1 +
 README.md           | 69 ++++++++++++++++++++++++++++++++++-----------
 lib/updateIn.js     | 11 ++++++++
 test/freeze-spec.js |  2 +-
 test/in-spec.js     | 35 +++++++++++++++++++++++
 5 files changed, 101 insertions(+), 17 deletions(-)
 create mode 100644 lib/updateIn.js
 create mode 100644 test/in-spec.js

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 419bf18..e1ddb20 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## [unreleased]
 * Add `u.freeze` to freeze an object deeply. (https://github.com/substantial/updeep/issues/7)
+* Add `u.in` to update a single value in an object with a specified path. (https://github.com/substantial/updeep/issues/6)
 
 ## [0.2.3]
 * Fix cannot update value to null (https://github.com/substantial/updeep/issues/8)
diff --git a/README.md b/README.md
index 7b5084e..47900bf 100644
--- a/README.md
+++ b/README.md
@@ -64,21 +64,25 @@ var newPerson = u({
 //    }
 ```
 
-### Simple update
+**NOTE**: All functions are curried, so if you see `f(x(, y))`, it can be called with either `f(x, y)` or `f(x)(y)`.
+
+### `u(updates(, object))`
+
+#### Simple update
 
 ```js
 u({ x: { b: 3 } }, { x: { a: 0, b: 0 } });
 // => { x: { a: 0, b: 3 } }
 ```
 
-### Multiple updates, including an array
+#### Multiple updates, including an array
 
 ```js
 u({ x: { b: 3 }, y: { 1: 4 } }, { x: { a: 0, b: 0 }, y: [0, 0] });
 // => { x: { a: 0, b: 3 }, y: [0, 4] }
 ```
 
-### Use a function
+#### Use a function
 
 ```js
 function inc(i) { return i + 1; }
@@ -86,7 +90,7 @@ u({ x: { b: inc } }, { x: { a: 0, b: 0 } });
 // => { x: { a: 0, b: 1 } }
 ```
 
-### Partial application
+#### Partial application
 
 ```js
 var setBTo3 = u({ b: 3 });
@@ -94,14 +98,53 @@ setBTo3({ a: 0, b: 0 });
 // => { a: 0, b: 3 })
 ```
 
-### Remove a property
+#### ES6 computed properties
 
 ```js
-u({ x: u.omit('b') }, { x: { a: 0, b: 0 } });
+var key = 'b';
+u({ x: { [key]: 3 } }, { x: { a: 0, b: 0 } });
+// => { x: { a: 0, b: 3 } }
+```
+
+### `u.in(path(, value)(, object))`
+
+Update a single value with a simple string or array path.
+
+```js
+u.in('a.b', 3, { a: { b: 0 } });
+// => { a: { b: 3 } };
+```
+
+```js
+function inc(i) { return i + 1; }
+u.in('a.b', inc, { a: { b: 0 } });
+// => { a: { b: 1 } };
+```
+
+```js
+u({
+  x: u.in(['a', 'b'], 3)
+}, { x: { a: { b: 0 } } });
+// => { x: { a: { b: 3 } } };
+```
+
+### `u.omit(predicate(, object))`
+
+Remove properties. See [`_.omit`](https://lodash.com/docs#omit).
+
+```js
+u({ x: u.omit('b') }, { x: { a: 0, b: 0, c: 0 } });
+// => { x: { a: 0, c: 0 } }
+```
+
+```js
+u({ x: u.omit(['b', 'c']) }, { x: { a: 0, b: 0, c: 0 } });
 // => { x: { a: 0 } }
 ```
 
-### Reject an item from an array
+### `u.reject(predicate(, object))`
+
+Reject items from an array. See [`_.reject`](https://lodash.com/docs#reject).
 
 ```js
 function even(i) { return i % 2 === 0 };
@@ -109,21 +152,15 @@ u({ x: u.reject(even) }, { x: [1, 2, 3, 4] });
 // => { x: [1, 3] }
 ```
 
-### With a default
+### `u.withDefault(default(, updates)(, object))`
+
+Like `u()`, but start with the default value if the original value is undefined.
 
 ```js
 u({ x: withDefault([], { 0: 3 }) }, {});
 // => { x: [3] }
 ```
 
-### ES6 computed properties
-
-```js
-var key = 'b';
-u({ x: { [key]: 3 } }, { x: { a: 0, b: 0 } });
-// => { x: { a: 0, b: 3 } }
-```
-
 See the [tests] for more examples.
 
 ## Install
diff --git a/lib/updateIn.js b/lib/updateIn.js
new file mode 100644
index 0000000..05dbc09
--- /dev/null
+++ b/lib/updateIn.js
@@ -0,0 +1,11 @@
+import curry from 'lodash/function/curry';
+import update from './update';
+
+function updateIn(path, value, obj) {
+  const parts = Array.isArray(path) ? path : path.split('.');
+  const updates = parts.reduceRight((acc, key) => ({ [key]: acc }), value);
+
+  return update(updates, obj);
+}
+
+export default curry(updateIn);
diff --git a/test/freeze-spec.js b/test/freeze-spec.js
index 6c89d22..1d84b6a 100644
--- a/test/freeze-spec.js
+++ b/test/freeze-spec.js
@@ -1,7 +1,7 @@
 import { expect } from 'chai';
 import freeze from '../lib/freeze';
 
-describe('freeze', () => {
+describe('u.freeze', () => {
   afterEach(() => {
     delete process.env.NODE_ENV;
   });
diff --git a/test/in-spec.js b/test/in-spec.js
new file mode 100644
index 0000000..96cc4cb
--- /dev/null
+++ b/test/in-spec.js
@@ -0,0 +1,35 @@
+import { expect } from 'chai';
+import updateIn from '../lib/updateIn';
+
+describe('u.in', () => {
+  it('can update a single path described with a string', () => {
+    const obj = { a: { b: 0 } };
+    const result = updateIn('a.b', 3, obj);
+    expect(result).to.eql({ a: { b: 3 } });
+  });
+
+  it('can update a single path described with a string with a function', () => {
+    const inc = x => x + 1;
+    const obj = { a: { b: 0 } };
+    const result = updateIn('a.b', inc, obj);
+    expect(result).to.eql({ a: { b: 1 } });
+  });
+
+  it('can update a single path described with an array', () => {
+    const obj = { a: { b: 0 } };
+    const result = updateIn(['a', 'b'], 3, obj);
+    expect(result).to.eql({ a: { b: 3 } });
+  });
+
+  it('can update arrays', () => {
+    const obj = { a: [0, 0, 0] };
+    const result = updateIn('a.1', 3, obj);
+    expect(result).to.eql({ a: [0, 3, 0] });
+  });
+
+  it('can be partially applied', () => {
+    const obj = { a: { b: 0 } };
+    const result = updateIn('a.b')(3)(obj);
+    expect(result).to.eql({ a: { b: 3 } });
+  });
+});