How to use custom-typed arguments in blocks

Question

I have defined a callback block for a JSON service like so:

#import "JSONResult.h"
typedef void (^JSONResultHandler)(JSONResult*);

Obviously, the JSONResult typed argument is a custom type and its header file is included where this block is defined. Why do I then get the following error?

/Users/oyvind/code/_objc/JSONService.h:22:35: Unknown type name 'JSONResult'

if you command+click on the JSONResult part, does it take you to the class's definition? — jere, Oct 19 '12 at 12:23
take a look at [this](http://stackoverflow.com/a/9633667/944634) — Parag Bafna, Oct 19 '12 at 12:37

score 3 · Accepted Answer · answered Oct 19 '12 at 12:46

Are you importing your JSON service class in JSONResult too? Maybe you have a circular reference problem.

If you are importing the JSON service class in JSONResult and that import is absolutely necessary, try using forward declaration to import JSONResult in your .h:

@class JSONResult;

@interface SomeJSONService : NSObject

typedef void (^JSONResultHandler)(JSONResult*);

@end

Double check your imports and class names are OK too.

Circular reference was the culprit. Thanks! – nordhagen Oct 22 '12 at 21:31 — nordhagen, Oct 22 '12 at 21:31

sergio · Answer 2 · 2012-10-19T12:28:32.013

0

Check that you have imported the JSONResult.h header correctly in JSONService.h:

#import "JSONResult.h"

edited Oct 19 '12 at 12:28

answered Oct 19 '12 at 12:22

sergio

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This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. – S.L. Barth is on codidact.com Oct 19 '12 at 12:25
@S.L. Barth: Thanks, I reworded the answer. – sergio Oct 19 '12 at 12:29

How to use custom-typed arguments in blocks

2 Answers2