How to call one constructor from another?

[Sheila Jones]

Hello,

Can somebody tell me how to do the following, please?

I have written a 'GridReference' class to encapsulate map locations. It has
a constructor that takes a couple of doubles, representing latitude and
longitude, i.e.
public GridReference(double latitude, double longitude) {
...
}

I now want to write another constructor that takes two strings. The strings
again contain latitude and longitude, but formatted as degrees, minutes and
seconds, for example: 52° 39' 27.246"N.

How do I write this second constructor so that it converts the strings to
the double equivalents (I can do that), then 'calls' the first constructor
with these values? Sort of like this:

public GridReference(string latitude, string longitude) {
double lat = ConvertToDouble(latitude);
double lng = ConvertToDouble(longitude);
//somehow jump to GridReference(lat, lng);
}

Thanks.

 

[Jon Skeet [C# MVP]]

Can somebody tell me how to do the following, please?

I have written a 'GridReference' class to encapsulate map locations. It has
a constructor that takes a couple of doubles, representing latitude and
longitude, i.e.
public GridReference(double latitude, double longitude) {
...
}

I now want to write another constructor that takes two strings. The strings
again contain latitude and longitude, but formatted as degrees, minutes and
seconds, for example: 52° 39' 27.246"N.

How do I write this second constructor so that it converts the strings to
the double equivalents (I can do that), then 'calls' the first constructor
with these values? Sort of like this:

public GridReference(string latitude, string longitude) {
double lat = ConvertToDouble(latitude);
double lng = ConvertToDouble(longitude);
//somehow jump to GridReference(lat, lng);
}

You'd do:

public GridReference(string latitude, string longitude)
: this (ConvertToDouble(latitude), ConvertToDouble(longitude))
{
}

IIRC, the ConvertToDouble method needs to be static.

 

[=?ISO-8859-2?Q?Marcin_Grz=EAbski?=]

Hi Sheila,

public GridReference(double latitude, double longitude) {

// body
}

public GridReference(string latitude, string longitude)

: this(ConvertToDouble(latitude), ConvertToDouble(longitude))

{

// double lat = ConvertToDouble(latitude);
// double lng = ConvertToDouble(longitude);
//somehow jump to GridReference(lat, lng);
// don't need to jump

}

Regards

Marcin

 

[Sheila Jones]

Thank you both for the quick replies! That's exactly what I wanted - and it
even works if ConvertToDouble is private! (although it has to be static?)

Can somebody tell me how to do the following, please?

I have written a 'GridReference' class to encapsulate map locations. It has
a constructor that takes a couple of doubles, representing latitude and
longitude, i.e.
public GridReference(double latitude, double longitude) {
...
}

I now want to write another constructor that takes two strings. The strings
again contain latitude and longitude, but formatted as degrees, minutes and
seconds, for example: 52° 39' 27.246"N.

How do I write this second constructor so that it converts the strings to
the double equivalents (I can do that), then 'calls' the first constructor
with these values? Sort of like this:

public GridReference(string latitude, string longitude) {
double lat = ConvertToDouble(latitude);
double lng = ConvertToDouble(longitude);
//somehow jump to GridReference(lat, lng);
}

You'd do:

public GridReference(string latitude, string longitude)
: this (ConvertToDouble(latitude), ConvertToDouble(longitude))
{
}

IIRC, the ConvertToDouble method needs to be static.

 

[Jon Skeet [C# MVP]]

Thank you both for the quick replies! That's exactly what I wanted - and it
even works if ConvertToDouble is private! (although it has to be static?)

Indeed - it being private isn't a problem at all. The reason it has to
be static is that it's being called effectively before the rest of the
object's state has a chance to "settle down" - so anything which *does*
rely on its state is probably broken.