Objective-c – Why can’t I switch an enum in Objective-C

enumsobjective cswitch statementxcode

I can't seem to figure out how I should use a switch statement with my custom typedef enum. Xcode tells this error:

Statement requires expression of integer type (MyEnum *) is invalid.

this is my enum declared over the @interface in my header

typedef enum {
  A, B, C, D, E, F, G,
  Ab, Bb, Db, Eb, Gb,
  CSharp, DSharp, FSharp, GSharp
} Tones;

this is my property:
@property(nonatomic) Tones *tone;

and this is my function to get the string value of the enum

- (NSString *)stringValue {

  switch (self.tone) {
    case GSharp:
      return @"G#";
    ...
  } 
}

Best Answer

An enum has literal values (basically named integers), not object pointers. Thus it should be:

@property(nonatomic) Tones tone;

Related Solutions

C# – How to cast int to enum

From an int:

YourEnum foo = (YourEnum)yourInt;

From a string:

YourEnum foo = (YourEnum) Enum.Parse(typeof(YourEnum), yourString);

// The foo.ToString().Contains(",") check is necessary for enumerations marked with an [Flags] attribute
if (!Enum.IsDefined(typeof(YourEnum), foo) && !foo.ToString().Contains(","))
{
    throw new InvalidOperationException($"{yourString} is not an underlying value of the YourEnum enumeration.")
}

Update:

From number you can also

YourEnum foo = (YourEnum)Enum.ToObject(typeof(YourEnum) , yourInt);

Python – Replacements for switch statement in Python

The original answer below was written in 2008. Since then, Python 3.10 (2021) introduced the match-case statement which provides a first-class implementation of a "switch" for Python. For example:

def f(x):
    match x:
        case 'a':
            return 1
        case 'b':
            return 2
        case _:        
            return 0   # 0 is the default case if x is not found

The match-case statement is considerably more powerful than this simple example.

You could use a dictionary:

def f(x):
    return {
        'a': 1,
        'b': 2,
    }[x]

Best Answer

Related Solutions

C# – How to cast int to enum

Python – Replacements for switch statement in Python

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