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Anonymous User

Anonymous User

20-Jul-2015

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.

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