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plurals

POClasses and Pointers, how do they work?
primarykey
Id
9106371
data
AcceptedAnswerId
0
AnswerCount
4
ClosedDate
CommentCount
7
CommunityOwnedDate
CreationDate
2012-02-02T02:31:04.980
FavoriteCount
1
LastActivityDate
2012-02-02T10:04:55.890
LastEditDate
2012-02-02T03:13:43.367
LastEditorUserId
556595
OwnerUserId
836781
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0
PostTypeId
1
Score
0
ViewCount
182
LastEditorDisplayName
text
Body
The main issue is with creating a dynamic class. What I did: <pre><code>ptr = new animal[2]; </code></pre> I'm trying to create a dynamic array of size 2, pointed by the pointer ptr. The issue arises when I try these operations: <pre><code>ptr[0].setspeed(9); ptr++->setspeed(13); </code></pre> I am using DDD (gdb graphical) debugger and when I display ptr, I only see it pointing to one object. When I try to set the speed, the first one seems to work, but the second one won't (the speed is on the default of 0). Printing only gets garbage. I am not so sure what's going on, please help. Also when I do: <pre><code>ptr->print(); </code></pre> Is it supposed to print for both <code>ptr[0]</code> and <code>ptr[1]</code>, or just <code>ptr[0]</code>? Also, can someone quickly draw a picture of how the <code>ptr</code> and new dynamic class look like? The way I see it, it is a ptr pointing to an array, array size of two, each one has an animal object. <pre><code>#include <iostream> using namespace std; class animal { private: int speed; double position_x; double position_y; public: animal() : speed(0), position_x(0), position_y(0) { } animal (int v, double x, double y) { this->speed = v; this->position_x = x; this->position_y = y; } animal(const animal & g) { this->speed = g.speed; this->position_x = g.position_x; this->position_y = g.position_y; } ~animal(); void print(); int getspeed() { return this->speed; } int getx() { return this->position_x; } int gety() { return this->position_y; } void setspeed(int s) { this->speed = s; } }; void animal::print() { cout << "speed: " << this->getspeed() << endl; cout << "position_x: " << this->getx() << endl; cout << "position_y: " << this->gety() << endl; } int main() { animal *ptr; ptr = new animal; ptr = new animal [2]; ptr[0].setspeed(9); ptr++->setspeed(13); ptr->print(); cout << ptr[0].getspeed() << endl; cout << ptr[1].getspeed(); return 0; } </code></pre>
Tags
<c++><pointers>
Title
Classes and Pointers, how do they work?
singulars
PostAcceptedAnswerId
1. This table or related slice is empty.
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USGustavo Mori
UserOwnerUserId
1. USRave
plurals
PostLinksPostIdRelatedPostId
1. PL
 singulars
 LinkTypeLinkTypeId
 LTLinked
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
3. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 POClasses and Pointers, how do they work?
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTApproveEditSuggestion
2. VO
 singulars
 PostPostId
 POClasses and Pointers, how do they work?
 UserUserId
 USPatrick Kennedy
 VoteTypeVoteTypeId
 VTFavorite
CommentsPostId

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