Dalam artikel ini, Anda akan belajar tentang berbagai fungsi yang ditentukan pengguna yang mengambil masukan dari berbagai jenis dan mengembalikan keluaran, dengan contoh.
Di artikel sebelumnya Fungsi Swift, kita belajar tentang fungsi. Sekarang, kita akan melihat berbagai cara dan tipe untuk membuat fungsi di Swift, yaitu menangani input dan output dalam suatu fungsi.
Fungsi tanpa parameter dan tanpa nilai kembali
Jenis fungsi ini tidak mengambil input dan mengembalikan nilai.
func funcname () (// pernyataan) OR func funcname () -> () (// pernyataan) ATAU func funcname () -> Void (// pernyataan)
Semua sintaks di atas valid untuk membuat fungsi yang tidak menggunakan parameter dan tidak mengembalikan nilai.
Sintaks di atas func funcname() -> ()juga sama dengan func funcname() -> Voidkarena Voidhanyalah tipe dari (). Anda dapat mengunjungi Swift Typealias untuk mempelajari lebih lanjut.
Contoh 1: Tidak ada Parameter yang lolos dan tidak ada nilai yang dikembalikan
func greetUser() ( print("Good Morning!") ) greetUser()
Ketika Anda menjalankan program di atas, hasilnya adalah:
Selamat pagi!
Fungsi tanpa parameter kecuali nilai kembalian
Jenis fungsi ini tidak mengambil parameter input apa pun tetapi mengembalikan nilai. Untuk menambahkan tipe pengembalian Anda perlu menambahkan panah ( ->) dan tipe pengembalian.
func funcname () -> ReturnType (// pernyataan nilai kembali)
Contoh 2: Tidak ada Parameter yang lulus tetapi mengembalikan nilai
func greetUser() -> String ( return "Good Morning!" ) let msg = greetUser() print(msg)
Ketika Anda menjalankan program di atas, hasilnya adalah:
Selamat pagi!
Dalam program di atas, Anda telah menentukan Jenis pengembalian menjadi String. Sekarang, pernyataan tersebut harus mengembalikan string dari pernyataan di dalam fungsi, jika tidak, Anda akan mendapatkan kesalahan.
returntransfer kata kunci kendali program dari badan fungsi ke pemanggilan fungsi. Jika Anda perlu mengembalikan nilai dari fungsi, tambahkan nilai setelah returnkata kunci.
return "Good Morning!"pernyataan mengembalikan nilai tipe Stringdari fungsi. Perhatikan bahwa jenis pengembalian dan nilainya harus cocok.
Anda juga dapat menetapkan nilai kembali ke variabel atau konstanta. let msg = memberikan nilai kembali ke pesan konstan. Jadi pernyataan itu print(msg)keluar dari Good Morning! di konsol.
Jika Anda ingin mengabaikan nilainya, Anda dapat menggunakan _as let _ =.
Fungsi dengan parameter tetapi tidak ada nilai kembali
Parameter digunakan untuk mengambil masukan dalam fungsi. Parameter berisi nama parameter dan tipe yang diikuti oleh titik dua ( :). Jenis fungsi ini mengambil parameter masukan tetapi tidak mengembalikan nilai.
func funcname (parameterName: Type) (// pernyataan)
Contoh 3: Parameter berhasil tetapi tidak ada nilai yang dikembalikan
func greetUser(msg:String) ( print(msg) ) greetUser(msg: "Good Morning!")
Ketika Anda menjalankan program di atas, hasilnya adalah:
Selamat pagi!
Dalam program di atas, fungsi tersebut menerima satu parameter tipe String. Parameter hanya dapat digunakan di dalam fungsi. msg adalah nama parameter.
Anda dapat memanggil fungsi tersebut dengan memberikan nilai string dengan nama parameter sebagai greetUser(msg: "Good Morning!"). Nama parameter msg hanya terlihat di dalam fungsi greetUser().
Oleh karena itu, pernyataan print(msg)keluar dari Good Morning! di konsol.
Berfungsi dengan parameter dan nilai kembali
Jenis fungsi ini mengambil parameter dan juga mengembalikan nilai.
func funcname (parameterName: Type) -> ReturnType (// pernyataan)
Contoh 4: Parameter lulus dan mengembalikan nilai
func greetUser(name:String) -> String ( return "Good Morning! " + name ) let msg = greetUser(name: "Jack") print(msg)
Ketika Anda menjalankan program di atas, hasilnya adalah:
Selamat pagi! Mendongkrak
Dalam program di atas, fungsi tersebut menerima satu parameter tipe Stringdan juga mengembalikan nilai Good Morning! Jack tipe String.
Berfungsi dengan banyak parameter dan beberapa nilai kembali
Jenis fungsi ini mengambil beberapa parameter yang dipisahkan oleh koma dan juga mengembalikan beberapa nilai. Anda dapat mengembalikan beberapa nilai di Swift menggunakan Tuple. Lihat Swift Tuple untuk mempelajarinya lebih lanjut.
func funcname(parameterName:Type, parameterName2:Type ,… ) -> (ReturnType, ReturnType… ) ( //statements )
Example 5: Multiple Parameters passed and multiple return value
func greetUser(name:String, age:Int) -> (String, Int) ( let msg = "Good Morning!" + name var userage = age if age < 0 ( userage = 0 ) return (msg, userage) ) let msg = greetUser(name: "Jack", age: -2) print(msg.0) print("You have (msg.1) coins left")
When you run the above program, the output will be:
Good Morning!Jack You have 0 coins left
In the above program, the function greetUser() accepts multiple parameters of type String and Int. The function also returns multiple values as a tuple of type String and Int.
To access each return value, we use index positions 0, 1,… Here, we've used msg.0 to access Good Morning!Jack and msg.1 to access 0.
Using index positions can be unintuitive and unreadable at times. We can solve this issue elegantly by giving names to return values. The above program can also be rewritten as below.
Example 6: Multiple return values with name
func greetUser(name:String, coins:Int) -> (name:String, coins:Int) ( let msg = "Good Morning!" + name var userCoins = coins if coins < 0 ( userCoins = 0 ) return (msg, userCoins) ) let msg = greetUser(name: "Jack",coins: -2) print(msg.name) print("You have (msg.coins) coins left")
In this program, the return type is of tuple that contains the variable name with the type. The main advantage of this is you can access the result using the variable name as msg.name and msg.coins instead of msg.0 and msg.1.
Function with argument label
When you define a function that accepts inputs, you can define the input name with the help of parameter name. However, there is another type of name which you can give along with the parameter name, known as argument label.
The use of argument labels allow a function to be called in an expressive way, sentence-like manner, while still providing a function body that is readable and clear in intent.
Each function parameter has both an argument label and a parameter name. By default, parameters use their parameter name as their argument label. But, if you explicitly define the argument name, the argument label is used when calling the function.
The syntax of function with argument label is
func funcname(argumentLabel parameterName:Type)-> Return Type ( //statements )
Let's see this in example below.
Example 7: Function without argument label
func sum(a:Int, b:Int) -> Int ( return a + b ) let result = sum(a: 2, b: 3) print("The sum is (result)")
When you run the above program, the output will be:
The sum is 5
In the above example, we have not specified the argument label, so it takes default parameter name a and bas the argument label while calling the function.
You may notice the function call is not expressive/sentence when calling the function. You may think it can be made more expressive as English if you could make the function call as:
let result = sum(of: 2, and: 3)
Now let's change the function as:
Example 8: Function with better function call but not as parameter names
func sum(of:Int, and:Int) -> Int ( return of + and ) let result = sum(of: 2, and: 3) print("The sum is (result)")
Now the method call is expressive. However, now we have to use the parameter name of & and in return of + and to find the sum of two numbers. Now, this makes the function body unreadable. Use of a and b instead of of&and would make more sense inside the function body.
For this purpose we have to explicitly define argument label as:
Example 9: Function with argument labels
func sum(of a :Int, and b:Int) -> Int ( return a + b ) let result = sum(of: 2, and: 3) print("The sum is (result)")
In the above program, the function accepts two parameter of type Int. The function call uses the argument label of & and which makes sense while calling the function as sum(of: 2, and: 3) instead of sum(a: 2, b: 3).
Also, the function body uses the parameter name a and b instead of of & and which also makes more sense while applying operations.
You can also omit the argument label by writing a _ before the parameter name.
func sum(_ a :Int, _ b:Int) -> Int ( return a + b ) let result = sum(2, 3) print("The sum is (result)")
Function with default parameter values
You can give default values for any parameter in a function by assigning a value to the parameter after that parameter's type. Giving a default parameter allows you to neglect the parameter while calling the function.
If you do not pass value to the parameter while calling the function, its default value is used. However, if you explicitly pass a value to the parameter while calling, the specified value is used.
func funcname(parameterName:Type = value) -> Return Type ( //statements )
Example 10: Function with default parameter values
func sum(of a :Int = 7, and b:Int = 8) -> Int ( return a + b ) let result1 = sum(of: 2, and: 3) print("The sum is (result1)") let result2 = sum(of: 2) print("The sum is (result2)") let result3 = sum(and: 2) print("The sum is (result3)") let result4 = sum() print("The sum is (result4)")
When you run the above program, the output will be:
The sum is 5 The sum is 10 The sum is 9 The sum is 15
In the above program, the function sum(of a :Int = 7 , and b:Int = 8) -> Int accepts two parameter of type Int but also specifies the default value of parameter a = 7 and b = 8.
If you pass value as a parameter in the function call as sum(of: 2, and: 3) then 2 and 3 is used instead of parameter default value.
But if you don't pass the parameter value as sum() , then default value 7 and 8 are used as the parameter value.
Function with variadic parameters
A variadic parameter can accept zero or more values of a specific type. You can specify variadic parameter by inserting three period characters (… ) after the parameter's type name.
You usually use a variadic parameter when you need to pass a varying number of input values to the parameter when the function is called. For example, a list of numbers, a list of alphabets, etc.
The syntax of function with variadic parameters is:
func funcname(parameterName:Type… ) -> Return Type ( //statements )
Example 11: Function with variadic parameters
func sum(of numbers:Int… ) ( var result = 0 for num in numbers ( result += num ) print("The sum of numbers is (result)") ) sum(of: 1, 2, 3, 4, 5, 6, 7, 8)
In the above program, the function sum(of numbers:Int… ) accepts a variadic parameter of type Int. A variadic parameter can accept multiple values separated by comma as sum(of: 1, 2, 3, 4, 5, 6, 7, 8).
The values 1, 2, 3, 4, 5, 6, 7, 8 passed as a variadic parameter are made available within the function's body as an array of the Int type. Therefore, we can apply for-in loop in the value as for num in numbers.
When you run the above program, the output will be:
The sum of numbers is 36
Note: Swift built in print() function also accepts variadic parameter of type Any.
Any represents to any data type in Swift e.g. Int, Float, Double,String etc.
Function with in-out parameters
When you define the function parameter, the function parameters cannot be modified inside the body. So they are constants by default. Let's see this in example:
func process(name:String) ( if name == ""( name = "guest" ) )
The above program results a compile-time error because you cannot change the value of a parameter.
If you want a function to modify a parameter's value, you need to define the parameter as in-out parameter. You write an in-out parameter by placing the inout keyword right before a parameter's type.
Behind the scenes, an in-out parameter has a value that is passed into the function, is modified by the function, and is passed back out of the function to replace the original value. Therefore the value passed in the function call cannot be a constant. You must declare it as a variable.
The syntax of function with inout parameter is:
func funcname(parameterName:inout Type) -> Return Type ( //statements )
Example 12: Function with in out parameter
func process(name:inout String) ( if name == ""( name = "guest" ) ) var userName = "" process(name: &userName) print(userName)
When you run the above program, the output will be:
guest
In the above program, we have declared a function that accepts inout parameter name so that the parameter can be changed/altered inside the body of the function.
You must use ampersand (&) sign directly before a variable's name when you pass argument to an in-out parameter so that it can be modified by the function.
