Title here
Summary here
Enums in Objective-C
Our code example demonstrates the use of enumerated types in a program. Here’s how it works in Objective-C.
#import <Foundation/Foundation.h>
typedef NS_ENUM(NSInteger, ServerState) {
StateIdle,
StateConnected,
StateError,
StateRetrying
};
NSString *ServerStateString(ServerState state) {
switch (state) {
case StateIdle:
return @"idle";
case StateConnected:
return @"connected";
case StateError:
return @"error";
case StateRetrying:
return @"retrying";
default:
[NSException raise:NSGenericException format:@"Unexpected ServerState."];
return @"";
}
}
ServerState transition(ServerState state) {
switch (state) {
case StateIdle:
return StateConnected;
case StateConnected:
case StateRetrying:
// Implement conditions to determine next state here
return StateIdle;
case StateError:
return StateError;
default:
[NSException raise:NSGenericException format:@"Unknown state: %ld", (long)state];
}
}
int main(int argc, const char * argv[]) {
@autoreleasepool {
ServerState state = StateIdle;
NSLog(@"%@", ServerStateString(state));
state = transition(state);
NSLog(@"%@", ServerStateString(state));
state = transition(state);
NSLog(@"%@", ServerStateString(state));
}
return 0;
}To run the program:
- Save the code in a file named
enums.m. - Compile the program using
clangorgcc.
$ clang -fobjc-arc -framework Foundation enums.m -o enums
$ ./enums
idle
connected
idleThe NS_ENUM macro defines the ServerState enum type with underlying NSInteger values. We also define a helper function ServerStateString to convert enum values to readable strings.
The transition function replicates state transitions for a server. It takes the current state and returns a new state based on predefined rules. If the state is unknown, it raises an exception.
Now that we’ve seen how to implement and use enums in Objective-C, we can look at more advanced topics in the language.