How do I do this?

Tom2012 · November 2012

This should be easy but I'm wracking my brains trying to do it. :-)

I want to put a set of co-ordinates into a table...

coords = {}

table.insert(coords, x1,y1)
table.insert(coords, x2,y2)
table.insert(coords, x3,y3)

What code is it to add the x,y to the table please?

Thank you

hgvyas123 · November 2012

try this method

local coords = {
{1,2},
{11,55},
{4,5},
{134,233},
}
print(coords[1][2])

or

local coords = {
{x=1,y=2},
{x=11,y=22},
{x=111,y=222},
{x=1111,y=2222},
}
print(coords[2].x)

Tom2012 · November 2012

Thanks I'm trying to use:

	for j=1,#layer.objects[i].polygon do
			myShape:lineTo(layer.objects[i].polygon[j].x,layer.objects[i].polygon[j].y)
 
			--local toInsert = layer.objects[i].polygon[j].x..','..layer.objects[i].polygon[j].y
 
table.insert(coords, layer.objects[i].polygon[j].x..','..layer.objects[i].polygon[j].y);

Then later..

poly:set(unpack(coords))

Tom2012 · November 2012

Something like that anyway ;-)

OZApps · November 2012

@tom, have you tried

coords = {}
 
table.insert(coords, {x1,y1})
table.insert(coords, {x2,y2})
table.insert(coords, {x3,y3})

You can find info like this and more in my book
Learn Lua for iOS Game Development from Apress at http://www.apress.com/9781430246626

Tom2012 · November 2012

Yep, but I need to be able to use:

poly:set(unpack(coords))

And for it to work like

poly:set(23,11,66,77,88,55,33,44)

I'm trying to feed coords dynamically into a table then read them into the poly:set box2d shape.

Thanks

Tom2012 · November 2012

You can use this:

table.insert(coords, x..","..y)

But of course you get the error:

main.lua:84: bad argument #1 to 'unpack' (table expected, got string)

OZApps · November 2012

@tom if you need to have them respond to unpack, then add them to the table, one at a time

 table.insert(coords,x)
 table.insert(coords,y)
 
 .
 .

Tom2012 · November 2012

Ah, this worked:

for loop

table.insert(x)
table.insert(y)

end for loop

then...

poly:set(unpack(coords))

OZApps · November 2012

@Tom, the issue could also be that you might have misunderstood unpack. Unpack will display the elements of an array, so the moment you make it a hashtable/dictionary object/key-value pair, it will not work.

So if you are expecting that unpack will unpack and return x=val, y=val, width=val, height=val, etc then you would head for massive disappointment.

But if you insert several values either all at once as

 table.insert(coords,{1,2,3,4,5,6,7,8,99}

or one by one as

 table.insert(coords,x)
 table.insert(coords,y)

remember, if you add more than one value using the {}, you are not adding a value but a new array/table to that index.

now if you use unpack(coords) it will work.

Tom2012 · November 2012

@tom if you need to have them respond to unpack, then add them to the table, one at a time
 table.insert(coords,x)
 table.insert(coords,y)
 
 .
 .

Ah you beat me to it. :-)

Thanks OzApps.

The stumbling block was I was thinking of pairs rather than individual numbers.

OZApps · November 2012

a little out of sync, glad that you got it resolved, if you need to understand unpack, you can read the above post.

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