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POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
 

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  1. POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
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    <p>I worked on this all day and am stuck on my logic in how I approached this problem. Whenever I have a <code>Vector&lt;class&gt; blah</code>. And I try to <code>blah.push_back(class())</code>, it doesn't, update or work.</p> <p>I've been researching and I think it has to do with pointers and references. I tried changing <code>Vector&lt;Student&gt; blah</code> to <code>Vector&lt;Student*&gt; blah</code>, and using 'new' <code>Student()</code> when I'm pushing it back, but it still yields the same result. I think I'm defining the vectors wrong.</p> <pre><code>#include "std_lib_facilities.h" using namespace std; class Student { public: string first_name; string last_name; string major; int student_id; Student() {}; Student(int no, string name1, string name2, string majorin) { first_name = name1; last_name = name2; student_id = no; major = majorin; } }; class Course { public: Vector&lt;Student&gt; Students; int max_enrollment; int course_id; string course_title; Course() {}; Course(int no_in,int max_in,string title_in) { max_enrollment=max_in; course_title=title_in; course_id=no_in; } }; unsigned int split(const std::string &amp;txt, vector&lt;std::string&gt; &amp;strs, char ch) { unsigned int pos = txt.find( ch ); unsigned int initialPos = 0; strs.clear(); // Decompose statement while( pos != std::string::npos ) { strs.push_back( txt.substr( initialPos, pos - initialPos + 1 ) ); initialPos = pos + 1; pos = txt.find( ch, initialPos ); } // Add the last one strs.push_back( txt.substr( initialPos, std::min( pos, txt.size() ) - initialPos + 1 ) ); return strs.size(); } class University { public: Vector&lt;Student&gt; studentlist; Vector&lt;Course&gt; courselist; University() {}; void Parse(string input) { //Case Statements vector&lt;string&gt; temp; split( input, temp, ' ' ); cout&lt;&lt;temp[0]; if (temp[0]=="S ") { //Add Student to University //Student* myStudent=new ); cout&lt;&lt;studentlist.size()&lt;&lt;endl; //Student(atoi(temp[1].c_str()),temp[2],temp[3],temp[4]) studentlist.push_back(Student()); } else if (temp[0]=="C") { //Add Course to University Course myCourse=Course(atoi(temp[1].c_str()),atoi(temp[2].c_str()),temp[3]); courselist.push_back(myCourse); } else if (temp[0]=="L") { //Add Student to Course list //Not Implemented-Find Course by temp[1] which is a int for (int i=0;i&lt;courselist.size();i++) { if (courselist.at(i).course_id==atoi(temp[1].c_str())) { courselist.at(i).max_enrollment=atoi(temp[1].c_str()); } } } else if (temp[0]=="A") { for (int i=0;i&lt;courselist.size();i++) { if (courselist.at(i).course_id==atoi(temp[1].c_str())) { for (int j=0;j&lt;studentlist.size();j++) { if (studentlist.at(j).student_id==atoi(temp[1].c_str())) { Student mystudent=studentlist.at(j); courselist.at(i).Students.push_back(mystudent); } } } } } else if (temp[0]=="D") { for (int i=0;i&lt;courselist.size();i++) { if (courselist.at(i).course_id==atoi(temp[1].c_str())) { for (int j=0;j&lt;courselist.at(i).Students.size();j++) { if (courselist.at(i).Students.at(j).student_id==atoi(temp[1].c_str())) { //Student mystudent=courselist.at(i).Students.at(j); courselist.at(i).Students.erase(courselist.at(i).Students.begin()+j); } } } } } else if (temp[0]=="PS") { cout&lt;&lt;"--Student Report--\n"; } else if (temp[0]=="PC") { cout&lt;&lt;"--Student Report--\n"; for (int i=0;i&lt;courselist.size();i++) { for (int j=0;j&lt;courselist.at(i).Students.size();j++) { string first_name=courselist.at(i).Students.at(j).first_name; string last_name=courselist.at(i).Students.at(j).last_name; string major=courselist.at(i).Students.at(j).major; //Waiting List var cout&lt;&lt;first_name&lt;&lt;" "&lt;&lt;last_name&lt;&lt;" "&lt;&lt;major&lt;&lt;"\n"; } } } } }; int main(int argc, char *argv[]) { string input; while(1==1) { cout&lt;&lt;"Command:: "; getline(cin,input); //cout&lt;&lt;input; University myUniversity; myUniversity.Parse(input); //Input is in the format X Name Name etc etc. Arguments separated by spaces cout&lt;&lt;"DEBUG:"&lt;&lt;myUniversity.studentlist.size(); } return 0; } </code></pre>
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      1. PTAnswer
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    1. PTQuestion
    1. USChristian Rau
    1. USCREW
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      1. LTLinked
    1. This table or related slice is empty.
    1. PO
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      1. POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI know what `std::vector` is, but what is `Vector`?
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      1. POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
      1. USFred Larson
    2. CO@FredLarson: Bjarne uses it in his book "Programming: Principles and Practice using C++". It's basically a vector with bounds checking. http://www.stroustrup.com/Programming/std_lib_facilities.h
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      1. POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
      1. USBenjamin Lindley
    3. COman, you're code is extremely unreadable
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      1. POWhat's wrong with my logic? My Vector or an object doesn't push_back a new object. Stays at size of 0
      1. USjuliomalegria
 

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