SWIFT – How do I get the parameter value of enumeration under IF?

switch parameter {
case .CaseA(let valueA):
 print(valueA)
}

if parameter == .CaseA(let valueA) {
 print(valueA)
}

enum Foo { 
 case A(Int)
 case B(String)
}

let parameter = Foo.A(42)

/* if case ... */
if case .A(let valueA) = parameter {
 print(valueA) // 42
}

/* switch ... */
switch parameter {
case .A(let valueA):
 print(valueA) // 42
case _: ()
)

See the answer in English> Get associated value from enumeration without switch/case 2
How to write this

switch parameter {
case .CaseA(let valueA):
 print(valueA)
}

As an If condition statement? This does not work:

if parameter == .CaseA(let valueA) {
 print(valueA)
}

If the situation is as follows, you can use

enum Foo {
 case A(Int)
 case B(String)
}

let parameter = Foo.A(42)

/* if case ... */
if case .A(let valueA) = parameter {
 print(valueA) // 42
}

If case pattern matching is equivalent to a switch that matches the empty (unused) default case Mode, for example,

/* switch ... */
switch parameter {
case .A(let valueA):
 print (valueA) // 42
case _: ()
)

For more information, please refer to the Language Reference – Patterns.