• Shriramana Sharma (22/22) Jan 01 2016 Hello. I'm trying the following code:
• SimonN (9/11) Jan 01 2016 The error should be in 'auto p = ...', not in the line using the
• John (9/30) Jan 01 2016 The error is actually referring to the lack of a suitable
• Shriramana Sharma (5/7) Jan 01 2016 Thanks Simon and John. First actual usage of D classes and mistaken
• Steven Schveighoffer (5/10) Jan 03 2016 class constructor requirements are much different from struct
• Jacob Carlborg (8/11) Jan 03 2016 To clarify, there's a default (implicit) constructor that initializes
• Steven Schveighoffer (7/16) Jan 04 2016 Technically, the GC initializes the data as given by the TypeInfo before...

Shriramana Sharma <samjnaa_dont_spam_me gmail.com> writes:

Hello. I'm trying the following code:

import std.stdio;
class TimeSpan
{
    immutable double start, end;
     property double length() { return end - start; }
}
void main()
{
    auto p = TimeSpan(1, 2);
    writeln(p.length);
}

...and I'm getting the error:

Error: no property 'opCall' for type '<src>.TimeSpan'

If I change the class to struct the  property is callable without parens but 
I need TimeSpan to be a class since I need to inherit from it.

http://dlang.org/property.html and 
http://dlang.org/spec/function.html#property-functions don't say anything 
about  property not being applicable for classes. 

Am I stuck with having to use the () for this even in D?

-- 

SimonN <eiderdaus gmail.com> writes:

On Friday, 1 January 2016 at 10:14:58 UTC, Shriramana Sharma 
wrote:
     auto p = TimeSpan(1, 2);
 Error: no property 'opCall' for type '<src>.TimeSpan'

The error should be in 'auto p = ...', not in the line using the 
property.

Instantiate with 'new TimeSpan(1, 2)' instead of 'TimeSpan(1, 
2)'. The latter would be the constructor call for a struct. 
Classes go on the GC'ed heap by default.

The property syntax should work. :-)

-- Simon

John <johnch_atms hotmail.com> writes:

On Friday, 1 January 2016 at 10:14:58 UTC, Shriramana Sharma 
wrote:
 Hello. I'm trying the following code:

 import std.stdio;
 class TimeSpan
 {
     immutable double start, end;
      property double length() { return end - start; }
 }
 void main()
 {
     auto p = TimeSpan(1, 2);
     writeln(p.length);
 }

 ...and I'm getting the error:

 Error: no property 'opCall' for type '<src>.TimeSpan'

 If I change the class to struct the  property is callable 
 without parens but I need TimeSpan to be a class since I need 
 to inherit from it.

 http://dlang.org/property.html and 
 http://dlang.org/spec/function.html#property-functions don't 
 say anything about  property not being applicable for classes.

 Am I stuck with having to use the () for this even in D?

The error is actually referring to the lack of a suitable 
constructor. It thinks TimeSpan should define opCall because of 
the way you're trying to create an instance your main function. 
It's nothing to do with the  property attribute. So you need to 
define a constructor. Also, use "new" when creating instances.

Alternatively, make it a struct and it will work as is without 
further changes.

Shriramana Sharma <samjnaa_dont_spam_me gmail.com> writes:

John wrote:

 It's nothing to do with the  property attribute. So you need to
 define a constructor. Also, use "new" when creating instances.

Thanks Simon and John. First actual usage of D classes and mistaken 
assumption that C++ syntax is valid. :-)

-- 

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 1/1/16 9:08 PM, Shriramana Sharma wrote:
 John wrote:

 It's nothing to do with the  property attribute. So you need to
 define a constructor. Also, use "new" when creating instances.

 Thanks Simon and John. First actual usage of D classes and mistaken
 assumption that C++ syntax is valid. :-)

class constructor requirements are much different from struct 
constructor requirements. There's also no implicit constructor that 
initializes all members as there is for structs.

-Steve

Jacob Carlborg <doob me.com> writes:

On 2016-01-03 18:48, Steven Schveighoffer wrote:

 class constructor requirements are much different from struct
 constructor requirements. There's also no implicit constructor that
 initializes all members as there is for structs.

To clarify, there's a default (implicit) constructor that initializes 
all members to what they are set to in the class declaration. But you 
cannot pass in any arguments to the default constructor. Hmm, 
technically that might actually not be the constructor that initializes 
the members, not sure.

-- 
/Jacob Carlborg

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 1/3/16 2:25 PM, Jacob Carlborg wrote:
 On 2016-01-03 18:48, Steven Schveighoffer wrote:

 class constructor requirements are much different from struct
 constructor requirements. There's also no implicit constructor that
 initializes all members as there is for structs.

 To clarify, there's a default (implicit) constructor that initializes
 all members to what they are set to in the class declaration. But you
 cannot pass in any arguments to the default constructor. Hmm,
 technically that might actually not be the constructor that initializes
 the members, not sure.

Technically, the GC initializes the data as given by the TypeInfo before 
the ctor is run. I believe the default ctor does nothing, not even sure 
if it exists or is called. For simplicity, you can assume there is one.

But yes, I was referring to the struct ctor that allows you to 
initialize one or more of the members to non-default values.

-Steve