Objective-C's switch statements only work on primitive types that are constant at compile time. However, many Objective-C APIs expect the developer to determine their behaviour based on identifiers passed in as NSString. This leads to many if ([identifier isEqualToSting:@"stringA"]) {...} else if ([identifier isEqual... blocks in code to deal with, for example, KVO or -prepareForSegue:sender:.

To deal with this, HCObjectSwitch adds a simple syntax that is very similar to the native switch statement. In order to avoid clashing with the native syntax, all keywords start with a capital letter.

HCObjectSwitch

Overview

A simple way to implement object based switch-like statements in Objective-C using blocks. Any object that conforms to NSCopying can be used to switched on.

Example

id inVariable = /* ... */;
__block id outVariable;

Switch (segue.identifier)
{
    Case (@"EmbedLoginViewController")
    {
        self.loginViewController = segue.destinationViewController;
        outVariable = @"Embed";

        FallThroughToDefault();
    }, // each case statement needs to be wrapped in parenthesees and terminated with a comma

    Case (@"ShowSettingsViewController")
    {
        HCSettingsViewController *settingsViewController = segue.destinationViewController;
        settingsViewController.delegate = self;
        settingsViewController.title = inVariable;

        outVariable = @"Show";

        FallThroughToDefault();
    },

    Default
    {
        // The _object_ object is the object that was used in the switch statement.
        // This is available automatically.
        NSLog(@"Segue '%@' triggered by: %@", _object_, sender);
    },
}; // The ; is required

Usage

The syntaxt for HCObjectSwitch is very close to the standard switch statement. All keywords start with a capital letter.

• Switch (object) Starts a switch clause on object
• Case (option) Code executed if the object matches option. This is implemented through blocks under the hood, thus when writing to variables in the enclosing scope they need to be __block.
• Default Code executed in the default case
• FallthroughTo(option) Fall through to the option case. Cases can be skipped.
• FallThroughToDefault Fall through to the default case. Cases can be skipped.

Parentheses after the Switch and Case statements are required, as is the comma at the end of the parenthesis.