How to make a copy of a dataset

Classic Servoy
1

Hi,

I would like to copy a Dataset, not make a reference to the same dataset

newDataset=oldDataset will not do because this will create a reference not a copy

any ideas ??

Regards,

2

Need to do a deep copy for arrays, objects and datasets. A couple of code samples:

  1. Dataset
/*
 *	TITLE    :	CODE_copy_dataset
 *			  	
 *	MODULE   :	rsrc_CODE_frameworks
 *			  	
 *	ABOUT    :	creates a copy of a dataset (not a reference), and returns it
 *			  	
 *	INPUT    :	dataset
 *			  	
 *	OUTPUT   :	copy of dataset
 *			  	
 *	REQUIRES :	
 *			  	
 *	MODIFIED :	Jul 2008 -- David Workman, Data Mosaic
 *			  	
 */

var original	= arguments[0]

var columns		= new Array()

for ( var i = 1 ; i <= original.getMaxColumnIndex() ; i++ ) {
	columns[i - 1] 	= original.getColumnName(i)
}

var deepCopyObj = databaseManager.createEmptyDataSet(0, columns)

for ( var i = 1 ; i <= original.getMaxRowIndex() ; i++ ) {
	deepCopyObj.addRow([i], columns.length)
	var row = original.getRowAsArray(i)
	for ( var j = 1 ; j <= row.length ; j++ ) {
		deepCopyObj.setValue(i, j, original.getValue(i, j))
	}
}

return deepCopyObj
  1. Arrays and objects. (Note the recursion for objects)
/*
 *	TITLE    :	CODE_copy_object
 *			  	
 *	MODULE   :	rsrc_CODE_frameworks
 *			  	
 *	ABOUT    :	creates a copy of an object (not a reference), and returns it
 *			  	
 *	INPUT    :	object
 *			  	
 *	OUTPUT   :	copy of object
 *			  	
 *	REQUIRES :	
 *			  	
 *	MODIFIED :	Mar 2008 -- Troy Elliott, Data Mosaic
 *			  	
 */

var origObj = arguments[0]

//if passed an array, create an array
if (origObj instanceof Array) {
	var deepCopyObj = new Array()
}
//if passed an object, create an object
else {
	var deepCopyObj = new Object()
}

for (var i in origObj) {
	if (typeof origObj[i] == 'object' && origObj[i] != null) {
		deepCopyObj[i] = globals.CODE_copy_object(origObj[i])
	}
	else {
		deepCopyObj[i] = origObj[i]
	}
}

return deepCopyObj
3

Hi David,

Thanks for the code samples.
I hoped there might be a simpler way to do this, but this will do the trick.

Regards,

4

Hi,

B.t.w for an Array there is an other option :

var oldArray = ["a", "b", "c"]; 
var newArray = oldArray.slice(); // makes an independent copy of oldArray
5

The array.slice() is a nice shortcut. One note – it doesn’t duplicate array properties. So if you do stuff like the following, you’ll need to use the custom deep copy method to get an accurate copy:

var x = new Array("a","b","c")
x.a = "apple"
x.b = "beer"
x.c = "can"

var xCopy = x.slice()

application.output(xCopy[xCopy[0]])
//output is null

var xDeepCopy = globals.CODE_copy_object(x)

application.output(xDeepCopy[xDeepCopy[0]])
//output is "apple"
6

There’s also this trick…

var clone = eval(obj.toSource());

Note also that the “slice()” solution for arrays will copy objects in the array by reference, I’m pretty sure.

greg.

7

Hi Greg,

Thanks !!

B.t.w. the slice() solution does not copy by reference, see example below

oldArray = ["a", "b", "c"]; 
var newArray = oldArray.slice(); 

oldArray[1]='xx'
newArray[1]='yy'

application.output(oldArray[0] + ' - ' + newArray[0])
application.output(oldArray[1] + ' - ' + newArray[1])
application.output(oldArray[2] + ' - ' + newArray[2])

the result is :

a - a
xx - yy
c - c

8

agiletortoise:
There’s also this trick…

var clone = eval(obj.toSource());

…

greg.

Great trick. Something new in 4.0.