What is the reason why the Go reflect package prints structure as an integer value?

In-depth analysis of the output of the structure of Go reflect package printing as integer value

This article analyzes the phenomenon of integer results when printing structures using reflect packages in Go language, and answers common questions.

In the example code, the reflect.ValueOf function gets the value of the interface variable age (integer 25). When printing reflect.TypeOf(age) (type) and reflect.ValueOf(age) (value), fmt.Println(t, v) outputs int 25 . This is not a simple integer output, t and v represent types and values, respectively.

The main questions include: (1) Does the reflect.Value structure implement reflect.Type interface? (2) Why fmt.Println(t, v) outputs int 25 , and why directly print reflect.Value to get the integer value 25.

First, reflect.Value does not implement reflect.Type interface. reflect.Type represents Go language type information, reflect.Value represents the value of the variable. The two concepts are different. t gets the type information of age ( int ), v gets the value of age (25).

Secondly, fmt.Println(t, v) outputs int 25 because fmt package special handling of reflect.Value type. The print series function of fmt will check first whether the parameter is of type reflect.Value . If so, print the underlying value held by reflect.Value directly, rather than the reflect.Value structure itself. Therefore, fmt.Println(v) actually prints the integer value 25 held by v , rather than the reflect.Value structure. This explains why a variable that looks like a structure is printed but gets an integer value.

Understanding the special processing mechanism of fmt package will help to clearly understand the interaction between reflect.Value and fmt package and explain the seemingly contradictory output results in the code. reflect.Value prints the underlying value it holds, not its structure information itself.

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