golang running error 216

Golang is a statically typed programming language that provides efficient memory management and concurrent programming capabilities. Therefore, it is widely used in web development, network programming, cloud computing and other fields. However, it is inevitable to encounter some running errors when developing applications using Golang. This article will focus on error code 216.

First of all, by consulting Golang official documents and related forums, we know that 216 errors are returned by functions. The value cannot be converted to the specified type. So, under what circumstances does this error occur? Let’s analyze them one by one.

1. The function return value type does not match the declared type
In Golang, the function should explicitly declare the return value type. If the return value type of the function does not match the declared type, error 216 will be returned. . For example, suppose we have a function foo that returns string type, but we declare its return value type to be int when declaring the function, then a 216 error will occur when the code is run.

2. The function return value is empty
The function in Golang can have no return value, but when we declare the return value type when declaring the function, but the function actually has no return value, Error 216 will also occur. For example, suppose we have a function bar that returns int type, but we do not use the return statement inside the function to return any value, that is, we do not return a value of int type, then a 216 error will occur when the code is run.

3. The function return value type is inconsistent with the type expected by the caller
Sometimes, when calling a function, the expected return value type does not match the actual function return value type, which will also cause error 216. For example, suppose we have a function baz that returns bool type, but we expect a return value of type int when calling the function, then a 216 error will be generated when the code is run.

In response to the above situations, we can solve them in the following ways:

1. Solution to the mismatch between the function return value type and the declaration type
When declaring a function, be sure to ensure that the return value The value type matches the actual return value type of the function. For example, if the foo function actually returns a value of type string, then its return type should be declared as string when the function is declared. If we have multiple return statements inside a function, the return value type in each return statement must be consistent with the declared type.

2. Solution to empty function return value
If the function itself does not need to return any value, then we can use a null return value when the function is declared, that is, return a null value. For example, when declaring a function bar that returns an int type, we can use the return 0; statement to return a null value. In this way, when the function is executed, even if there is no specific return value, no 216 error will be generated. At the same time, you also need to pay attention when calling a function. If you expect a return value, you need to ensure that there is a specific return statement inside the function.

3. Solution to the inconsistency between the function return value type and the caller’s expected type
If the function’s actual return value type is inconsistent with the caller’s expected type, you can consider adding a type conversion operation when calling the function to convert the function The return value is converted to the type expected by the caller. For example, when calling the function baz that returns bool type, we can use the following code to perform type conversion:

result := baz()
if result == true {
    i := 1 //int类型
    fmt.Println(i)
} else {
    i := 0 //int类型
    fmt.Println(i)
}

In this way, even if the actual return value type of the function is bool type, it can be correctly converted when the code is running. Convert to the int type expected by the caller.

Summary:
Runtime error 216 in Golang is caused by the function return value type being unable to be converted to the specified type. It is mainly divided into the following situations: the function return value type does not match the declared type, the function returns The value is empty, and the function return value type is inconsistent with the type expected by the caller. For these situations, we can solve it by ensuring that the function return value type is consistent with the declared type, using a null return value, or performing type conversion. When writing Golang code, we should read the function declaration carefully and ensure that the return value type is consistent with the expected value type when calling the function to avoid runtime errors.

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