Key-Value Observing – fixed typo in unsubscribing section
Add notification handling to iCloud key-value storage notification
Fixed AVCaptureMetaDataOutput example in iOS 7 article

It is only hinted at in the documentation, but you cannot set `metadataObjectTypes` until the `AVCaptureMetaDataOutput` is associated with a session.

From the docs on `metadataObjectTypes`:

> When assigning a new array to this property, each of the type strings must be present in the array returned by the availableMetadataObjectTypes property; otherwise, the receiver raises an NSException.

and from the docs on `availableMetadataObjectTypes`:

> The available types are dependent on the capabilities of the AVCaptureInputPort to which the receiver’s connection is attached.

I was running the code as-is, and getting exceptions, so I found this SO answer http://stackoverflow.com/a/18995305/196358 which suggested adding the AVCaptureMetaDataOutput to a session before assigning the metadataObjectTypes. It solved my problems.
correct typo
insert missing word
correct grammar
correct grammar
more conventional method formatting
use proper … character
Add missing word (grammar)

A `static` variable declared globally can called -> A `static` variable declared globally can be called
Fixed @autorelease typo
Update 2012-08-20-nsoperation.md

Delete extra of
- wrong type in file listing example

contentsOfDirectoryAtURL:includingPropertiesForKeys:options:error:
returns an array of NSURLs not NSString
Fixing method reference /cc @davedelong
Minor grammatical and formatting fixes
Fixing typo /thanks @bdmontz
Merge pull request #61 from neilkimmett/master

Remove unnecessary "to" in NSNotificationCenter article
Merge pull request #58 from rskuja/typo_fix

Fixed @autorelease typo
Merge pull request #59 from ScottPetit/patch-1

Remove extra of in 2012-08-20-nsoperation.md
Merge pull request #53 from mikeabdullah/patch-2

Assorted typo, grammar, and formatting fixes