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iOS Build a Self-Destructing Message iPhone App Relating Users in Parse.com Adding the Edit Friends Screen

Posted by Alex Cevallos
Alex Cevallos
16,551 Points

Difficulty understanding iOS Blocks, help

hello I have resolved the issue, thanks

2 Answers

Patrick Serrano
Patrick Serrano
13,834 Points
Patrick Serrano
Patrick Serrano
13,834 Points

They are passing the block as the method parameter. I'll try to break it down for you since blocks can be a little confusing:

In the example you posted you are calling findObjectsInBackgroundWithBlock: on the query object.

The findObjectsInBackgroundWithBlock: method takes a block as a parameter.

The block you are passing into findObjectsInBackgroundWithBlock: has two parameters (NSArray *objects, NSError *error)

Inside the block you are writing an if statement. (the if statement is being used to check for an error before executing the code that you're trying to execute with the block.)

There are a few different places and ways to call block and they have slightly different syntaxes. You can take a look at Fucking Block Syntax for examples of the most common syntaxes.

Alex Cevallos
Alex Cevallos
16,551 Points

Hey thank you for the help! I looked at that site you sent and couldn't find the syntax for findObjectsInBackgroundWithBlock ? The documentation says link The block should have the following argument signature:(NSArray objects, NSError error). Does that mean you just attach the arguments to the method?

thanks again

Alex Cevallos
Alex Cevallos
16,551 Points
Alex Cevallos
Alex Cevallos
16,551 Points

accidental comment

Patrick Serrano
Patrick Serrano
13,834 Points
Patrick Serrano
Patrick Serrano
13,834 Points

I can't reply to your reply so I'll do it here, but the site I linked to just shows the syntax for blocks generically. It isn't for a specific method or anything like that, but instead meant to be a place to look to when you're looking to write your own block. I'm not 100% sure what you mean when you say "Does that mean you just attach the arguments to the method?"

The findObjectsInBackgroundWithBlock: method returns an NSArray, which is then passed into the block with the parameter name objects for you to use. In the video for this part of the course you see in the else block, the property self.allUsers is set equal to objects.