Constructor of Structs.
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Hi, Can somebody tell me what are all the limitations of the constructor of a struct? Is it possible to declare an ordinary writeline statement in its constructor?
Regards, Lenus.
Limitation is that structs cannot contain explicit parameterless constructors. But you certainly can use Console.WriteLine in sturct's constructor. See this example:
using System; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Test t = new Test(7); Console.ReadLine(); } } public struct Test { public Test(int x) { Console.WriteLine("I'm Test's constructor and this is my x parameter: "+ x.ToString()); } } } -
Limitation is that structs cannot contain explicit parameterless constructors. But you certainly can use Console.WriteLine in sturct's constructor. See this example:
using System; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Test t = new Test(7); Console.ReadLine(); } } public struct Test { public Test(int x) { Console.WriteLine("I'm Test's constructor and this is my x parameter: "+ x.ToString()); } } } -
Yes it is possible only if the struct is instantiated (as if it was an object). Not in the other case when we declare it without the new operator(as if it was a value type variable). Any suggestions?
Regards, Lenus.
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Yes it is possible only if the struct is instantiated (as if it was an object). Not in the other case when we declare it without the new operator(as if it was a value type variable). Any suggestions?
Regards, Lenus.
SPanicker* wrote:
Not in the other case when we declare it without the new operator(as if it was a value type variable).
Now I know what you were asking, it was not clear from your initial post. In that case, default parameterless constructor is called and as I said before you cannot declare or override paremeterless constructor.
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No I just want to print out something from the struct's constructor which is not happening. Why is it so?
Regards, Lenus.
Go forth and try it.
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SPanicker* wrote:
Not in the other case when we declare it without the new operator(as if it was a value type variable).
Now I know what you were asking, it was not clear from your initial post. In that case, default parameterless constructor is called and as I said before you cannot declare or override paremeterless constructor.
Even in this case, the constructor(which i provide) is getting read and the values are assigned. Only exception is that,I cannot call any other functions from inside that( But values can be assigned to variables ). I still need two points to be cleared: As you said if the parameterless constructor cannot be overridden then how is this happening? If the parameterless constructor cannot be overriden, then why is C# designed to accept such constructors which are of no use? Thanks.
Regards, Lenus.
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Go forth and try it.
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Even in this case, the constructor(which i provide) is getting read and the values are assigned. Only exception is that,I cannot call any other functions from inside that( But values can be assigned to variables ). I still need two points to be cleared: As you said if the parameterless constructor cannot be overridden then how is this happening? If the parameterless constructor cannot be overriden, then why is C# designed to accept such constructors which are of no use? Thanks.
Regards, Lenus.
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You declare(override) parameterless constructor? I'm lost here, can you past piece of code with your struct?
Hi Michal, Sorry what i meant was, I have a constructor for a (value type - declared without new keyword) struct. This constructor cannot invoke any inbuilt functions like Console.WriteLine or user defined ones. But at the same time it can do assign values for fields. This seems quite strange. But, the same things works well(from inside the constructor)if it is declared with the new keyword. Pls. chk this sample code and tell me if somethngs wrong:
using System; struct newStruct { //case 1: With struct new operator public newStruct(int a) { Console.WriteLine("In newStruct"); Console.WriteLine("{0}",a); } } struct anotherStruct { //case : Without new operator - like a value type variable. public int x; public anotherStruct(int a) { Console.WriteLine("In newStruct"); x = a; Console.WriteLine("{0},{1}",a,x); } public void method1() { Console.WriteLine(x); } } class AppEntry { public static void Main() { newStruct abc = new newStruct(10); anotherStruct def; def.x= 250; def.method1(); } }Regards, Lenus.
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Hi Michal, Sorry what i meant was, I have a constructor for a (value type - declared without new keyword) struct. This constructor cannot invoke any inbuilt functions like Console.WriteLine or user defined ones. But at the same time it can do assign values for fields. This seems quite strange. But, the same things works well(from inside the constructor)if it is declared with the new keyword. Pls. chk this sample code and tell me if somethngs wrong:
using System; struct newStruct { //case 1: With struct new operator public newStruct(int a) { Console.WriteLine("In newStruct"); Console.WriteLine("{0}",a); } } struct anotherStruct { //case : Without new operator - like a value type variable. public int x; public anotherStruct(int a) { Console.WriteLine("In newStruct"); x = a; Console.WriteLine("{0},{1}",a,x); } public void method1() { Console.WriteLine(x); } } class AppEntry { public static void Main() { newStruct abc = new newStruct(10); anotherStruct def; def.x= 250; def.method1(); } }Regards, Lenus.
Hi Lenus, there is nothing wrong with your code. In struct newStruct you defined constructor with parameter that is called when you create instance of newStruct:
newStruct abc = new newStruct(10);In struct anotherStruct you also defined constructor with parameter, but this constructor is never called.anotherStruct def;//here you create object def of type anotherStruct. no costructor is calleddef.x = 250;// here you just assign value 250 to variable x, no constructor is calleddef.method1();//this writes 250 to output which is totally correct since you set x to 250 before Compiler won't compile code if you do not set def.x. I was probably wrong when I said there is default parameterless constructor. There is no default parameterless constructor at all and you can not declare your own. -
Hi Lenus, there is nothing wrong with your code. In struct newStruct you defined constructor with parameter that is called when you create instance of newStruct:
newStruct abc = new newStruct(10);In struct anotherStruct you also defined constructor with parameter, but this constructor is never called.anotherStruct def;//here you create object def of type anotherStruct. no costructor is calleddef.x = 250;// here you just assign value 250 to variable x, no constructor is calleddef.method1();//this writes 250 to output which is totally correct since you set x to 250 before Compiler won't compile code if you do not set def.x. I was probably wrong when I said there is default parameterless constructor. There is no default parameterless constructor at all and you can not declare your own.