C++载体不能push_back

Question

我不知道是什么导致了这个错误：

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资料来源如下：

#include <iostream>
#include <vector>

using namespace std;

class taco {
private:
    //Classes
    class ingredient {
        private:
            //Ingredients have basic flavors
            //Flavors should total 100% for ingredients
            float sweet;
            float sour;
            float bitter;
            float salt;
            float umami; //Difficult taste to define, generally synonomous with savory or meaty
            //Ingredients have flavor modifiers
            bool hot; //Is the ingredient served Hot or Cold?
            short intensity; //How bland is the ingredient (100% for flavorful, 0% for flavorless)
            short moist; //100% for liquid (sauces etc) higher % to represent juice meats or fruits
        public:
            ingredient ( float sweet = 30.0, float sour = 0.0, float bitter = 0.0, float salt = 60.0, float umami = 10.0, bool hot = false, float intensity = 30.0, float moist = 25.0) {
                //Default ingredient is flour tortilla
                this->sweet = sweet; //Grains typically have a sugary tast even though it might not be very strong
                this->sour = sour;
                this->bitter = bitter;
                this->salt = salt; //Tortillas do have a salt content as well, it might not be very strong but this 60% represents a total out of the 100% flavor, the strength is determined by intensity
                this->umami = umami; //Most foods have at least small amounts of umami. Its umami that gives two foods with similliar tastes, different flavors. 
                this->hot = hot; //While a steamed tortilla is good, tortillas can be served either steamed or unsteamed. We default to not steamed as steamed tortilla will be a different ingredient
                this->intensity = intensity; //Tortillas are relatively bland. They have a destinctive taste and can affect the overall taste of a taco but the taste is not very intense
                this->moist = moist; //Flour tortillas are not generally moist but if there was no water content they would be brittle and unbending. Steamed tortillas and corn tortillas are usually more moist.
            }
    };

    //Vectors
    vector<ingredient> ingredients; //Create vector to store ingredients

public:
taco () {
    ingredient defIngredient();
    this->ingredients.push_back(defIngredient);
}

void foo ( ingredient bar ) {
    this->ingredients.push_back(bar);
}

};

int main ( void ) { 
return 0;
}

我对向量的经验基本上没有，但我不明白为什么它说它不能转换类型。向量被定义为类型成分，我试图推送给它的值也是相同类型的。

编辑:我很抱歉，这不是我想发布的错误，我只是更新了一下。之前的代码是在玩了一些东西之后。我确实意识到，在int类型的帽子代码中存在着差异。

Answer 1

一个常见的错误：

ingredient defIngredient();

不是用空构造函数初始化。

使用

ingredient defIngredient; 

而不是。这是唯一的例外，非常令人讨厌和容易被忽视。

若要避免再次落入该陷阱，请使用新的{...}**-syntax**.初始化C++11和。

ingredient defIngredient{};

不管怎么说。考虑在构造函数中使用初始化器：

class ingredient {
    private:
...
        ingredient()
          : sweet(30.0), sour(0.0), bitter(0.0), salt(60.0), umami(10.0),
            hot(false), intensity(30.0), moist(25.0)
          {}

或使用C++11 成员初始化器

class ingredient {
    private:
        float sweet = 30.0f;
        float sour = 0.0f;
        float bitter = 0.0f;
        float salt = 60.0f;
        float umami = 10.0f;
        bool hot = false;
        short intensity = 30;
        short moist = 25;
 }; // no default c'tor needed anymore

说到C++11：

更好的老C++是：

void foo ( const ingredient& bar ) {
    this->ingredients.push_back(bar);
}

这可能会给你节省一份对象。

在C++11中，van对参数使用值语义(这总是一件好事)，并且仍然保存副本--但是使用上面的const，您已经达到了90%的效果。

void foo ( ingredient bar ) {
    this->ingredients.emplace_back(std::move(bar));
}

也许这会让你对C++有所提升。

Answer 2

ingredient.是一个vector<ingredient*>，如您所见，它包含指向vector<ingredient*>的指针。您正试图向后推bar，即a本身。

您不能只做&bar (很好，它会编译，但不会工作)，因为bar是一个本地对象，很快就会被销毁。

相反，您应该将ingredient对象存储在矢量中：

vector<ingredient> ingredients;

Answer 3

您有指针向量，您尝试push_back的不是一个指向成分的指针，而是一个成分对象。从将vector<ingredient*> ingredients;更改为vector<ingredient> ingredients;开始。