WHAT IS MESSAGING?

Jayne Spooner

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  1. Jayne Spooner

    Post:3

    Points:15
    What is messaging?

    Messaging is the terminology for invoking methods on an object. The format for a message expression is as follows (the brackets are required):

    [object method]

    or in Objective-C parlance

    [receiver message]

     

     Simple example:

    // Create an instance of SomeClass object
    

    SomeClass *ptr = [[SomeClass alloc] init];

    // Send the message 'printInstanceVars' to the 'ptr' receiver

    [ptr printInstanceVars];

     

    If we want to pass an argument as part of the message (that is, pass a parameter to the method), we send a message that looks like this:

    [receiver message:argument]

    For example, assume setStr and setX are two methods in the SomeClass object and ptr is a pointer an instance of SomeClass . Here is how we might pass arguments to each method.

    [ptr setStr:@"Testing"];

    [ptr setX:2008];

    Side note: The @ symbol at the front of @”Testing” string is convenience method that converts the given string to an NSString object, which in the case of the setStr method, is the required type for the parameter.

      Modified On Jul-20-2015 03:28:05 AM

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