Welcome to the Treehouse Community
Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.
Looking to learn something new?
Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.
Start your free trial
jas cheema
823 Pointsthird parameter in the constructor
I can not understand why Map map is passed to MapLocation constructor
public MapLocation(int x, int y, Map map): base(x,y);
2 Answers
Allan Clark
10,810 PointsMap is needed in the constructor to verify that the x and y parameters are valid. The constructor tests that (x,y) coordinate is on the map passed in. Don't worry about the error he was talking about, he was referring to using the keyword 'this'. The OnMap method needs an x and y on the Point passed to it, the video means you will not get an error by passing 'this' to OnMap because the base constructor will have already run.
William Harrison
9,585 PointsThere is a couple ways to look at the use of Map.map. First, you are looking for a map location, so you need a map to verify against. Second, OnMap is a method of the Map class, so you need an instance of Map to call OnMap.
jas cheema
823 PointsI don't understand at all. how can we pass an object of class to constructor? according to video it was to violate something to invoke default constructor.Can you please explain in details ?
jas cheema
823 Pointsjas cheema
823 PointsThanks a lot Allan. But sorry I am still confused. Can you please explain with an example?
Allan Clark
10,810 PointsAllan Clark
10,810 PointsFor instance you can't make a MapLocation at (12, 14) if the map is only a 10x10 map. You would need have the map before you created the location, so the easiest way to check that is in the constructor.