Always hint when using vector: Can't evaluate the value of expression? ? ?

zeaphur

I declare a container type in the header file
typedef std :: vector <int> CityRouterDef;
Then define a class to contain this container
class Population
{
...
CityRouterDef PopIndex;
...
}
Excuse me:
1 Do you need to initialize popIndex in the constructor of the population?
How to write it if needed?
2 I defined the population array later. When population is empty, for example, when popIndex in population [0] is empty, I monitored it and found that the data of popIndex indicates that the value of the expression cannot be calculated. Isn't popIndex initialized? ? But what about popIndex in non-empty population? ? Be puzzled, please give pointers! !!

julines

CityRouterDef is a vector <int> variable. How can it be used as a type?

julines

Ah sorry to read it wrong

hzxszmh

Can be initialized
Population :: Population (): PopIndex (32) size initialization
Population :: Population (): PopIndex (iterator1, iterator2) // Iterator
Wait

When there is no data, of course you cannot use population [0].

food0012

Generally, only the basic types of data need to be initialized. Generally, wrapped objects have their own initialization process.

zeaphur

population [0] is an object array element, and popIndex is a member of the object element. According to theory, vector is a system construct that calls the default initialization function, that is, an empty container is constructed, but there should not be a value that cannot be calculated Such a mistake? I know I can't call non-existent data, but is there anything wrong with an empty container?