nlohamman json jstar[key]=value; no viable overloaded ‘=‘

Question

是什么原因？

The error message “no viable overloaded ‘=’ “ in the context of NLohamman’s JSON library (or any C++ code) typically means that you are trying to assign a value to an object or variable, but the compiler can’t find a suitable assignment operator for that particular operation.

In the case of jstar[key]=value;, it seems like you’re trying to assign a value to a key in a JSON object using syntax similar to JavaScript. However, JSON manipulation in C++ libraries usually doesn’t use this kind of syntax directly.

NLohmann’s JSON library (nlohmann/json) provides functions such as operator[] for accessing and assigning values, but not with the exact syntax you’ve used. Here’s how you’d set a value with a string key in his library:

#include <nlohmann/json.hpp>
using json = nlohmann::json;

// ...

json jstar;
jstar["key"] = value; // where 'value' is the data you want to insert

Make sure value is a type that can be converted into a type supported by the JSON library, such as int, double, std::string, bool, or another json object.

Answer 1

该回答引用自GPT-3.5,由博主GISer Liu编写：

针对你提出的问题，错误信息"no viable overloaded '=' "通常意味着你试图给一个对象或变量赋值，但编译器找不到适当的赋值运算符来执行这个操作。在你的情况下，似乎你正在尝试使用类似JavaScript的语法给JSON对象中的键赋值。然而，在C++库中操作JSON通常不直接使用这种语法。

nlohmann/json库提供了operator[]等函数来访问和赋值数值，但不是用你使用的确切语法。下面是如何在该库中使用字符串键设置数值的方法：

#include <nlohmann/json.hpp>
using json = nlohmann::json;

// ... 

json jstar;
jstar["key"] = value; // 这里的'value'是你想要插入的数据

确保value是一种可以转换为JSON库支持的类型，比如int、double、std::string、bool或另一个json对象。

这样，你可以按照这种方式修改你的代码，以解决该错误。

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