When linking with external dylib for an Xcode project. You might get this error:

Xcode 4.0 solution

1) click on the project in the side pane to bring up the properties.

2) click on "Target"

Checking the library:

3) In "Build Settings"

4) Using search, enter "library". There should be a path automatically set in the field for "Library Search Paths" if you added the dylib to your project.

Add a copy files phase:

3) In "Build Phases"  

4) Click "Add Build Phases"

5) Click "Add Copy Files"

6) In "Destination" select "Executables"

7) Add entry by clicking the "+"

8) Choose the .dylib file from your project or manually locate it.