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digitalmars.D.learn - constructor is not callable using argument types ()

reply "Suliman" <evermind live.ru> writes:
I am learning D classes and I am getting error when I am try to 
make instance of class. erorr:
C:\code\main.d(9): Error: constructor 
GetFileName.GetFileName.this (string name) is not callable using 
argument types ()

http://www.everfall.com/paste/id.php?xie09xz9upth
Dec 06 2012
next sibling parent "Simen Kjaeraas" <simen.kjaras gmail.com> writes:
On 2012-12-06, 20:17, Suliman wrote:

 I am learning D classes and I am getting error when I am try to make  
 instance of class. erorr:
 C:\code\main.d(9): Error: constructor GetFileName.GetFileName.this  
 (string name) is not callable using argument types ()

 http://www.everfall.com/paste/id.php?xie09xz9upth

You have supplied the string you promised to. You have this constructor: this(string name) And call it like this: new GetFileName(); Where's the string the constructor expects? Instead, you should call it like thus: new GetFileName("test"); -- Simen
Dec 06 2012
prev sibling next sibling parent "Suliman" <evermind live.ru> writes:
Am I right that my variant of code would be valid for C#?

How can I assign value to name in such manner?
Dec 06 2012
prev sibling next sibling parent "Suliman" <evermind live.ru> writes:
When I should use keyword this?
I dropped it from my class and now I can make instance of class 
without in sych way:

auto file = new GetFileName();
file.name = "test";
Dec 06 2012
prev sibling next sibling parent "Simen Kjaeraas" <simen.kjaras gmail.com> writes:
On 2012-12-06, 20:48, Suliman wrote:

 When I should use keyword this?
 I dropped it from my class and now I can make instance of class without  
 in sych way:

 auto file = new GetFileName();
 file.name = "test";

Indeed. If you have not defined a constructor, the language defines one for you, which is parameterless. It does nothing but allocate and initialize memory. The moment you define a constructor of your own, the compiler decides you probably want to define the parameterless constructor yourself, or not at all, and thus does not define it for you. If you want both, then define both: class MyClass { string name; this() { name = "Foo!"; } this(string name) { this.name = name; } } -- Simen
Dec 06 2012
prev sibling next sibling parent "Suliman" <evermind live.ru> writes:
Could you help me with this simple code. I still playing with 
constructor, but I can't understand how to use it.
http://www.everfall.com/paste/id.php?6n72xxxkz7ba
Dec 08 2012
prev sibling next sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Suliman:

 Could you help me with this simple code. I still playing with 
 constructor, but I can't understand how to use it.
 http://www.everfall.com/paste/id.php?6n72xxxkz7ba

You have code like this: class FileName { string name; this(string name) { this.name = name; } ... void ReadFile() { auto file = new FileName(); ... As you see you define a costructor that accepts a string, but then when you allocate the class you don't give it a string. So the correct code is: void ReadFile() { auto file = new FileName("somestring"); ... More notes: - By convention in D method/function names start with a lower case. - Don't indent module-level functions (like ReadFile). - If your program is composed by more than one module, I suggest to add a name at the top of the imported module, like "module Foo;". - In D structs are used quite often. Bye, bearophile
Dec 08 2012
prev sibling next sibling parent "Suliman" <evermind live.ru> writes:
Thanks!

But if I have a lot of property like^
string name
int age
....

it's not good to specify all of them in paranceses:
auto file = new FileName("test.txt", 21, ETC);

How can I specify them in another way?
Dec 10 2012
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Suliman:

 But if I have a lot of property like^
 string name
 int age
 ....

 it's not good to specify all of them in paranceses:
 auto file = new FileName("test.txt", 21, ETC);

 How can I specify them in another way?

There are several ways to help that. A simple way is to use default arguments: this(string fileName, int id=21, Foo f=ETC) {...} An alternative is to define various constructors with different number of arguments. Other solutions include the use of a little configuration struct, or the chaining of setters that return "this": FileName setId(int id_) { this.id = id_; return this; } Then if you define several of such setters, you can chain only the ones you want in a single line. auto f = new FileName("test.txt"); f.setId(21).setF(ETC); Probably there are other solutions. Bye, bearophile
Dec 10 2012