php editor Zimo is here to introduce a common code fragment: f = Foo(value). What this code does is creates a Foo object named f and passes value as a parameter to its constructor. In this way, we can use the Foo object in the program and operate and process it. A Foo object may be an instance of a class, which may have various properties and methods used to implement specific functionality. By creating an object and passing parameters, we can dynamically initialize the object's properties as needed to meet the program's requirements. This is a commonly used code snippet that can be used in many different programming scenarios.

Question content

I found the implementation of thedatabase/sql.Scannerinterface, but I don’t quite understand it?

can be compiled

The part I get isFoois an integer and it has methodScan

1. Scanmethod returnserror, but how to returnfmt.Errorf("Invalid database type: %T %v", value, value)? Isn't this a bug or is it?

2. *f = Foo(value)What does it do? When you pass this type torows.Scan(), does it callFoo.Scan()? If the type is expectedint64it will call itselfFoo(value)?

Code

type Foo int // Scan implements the database/sql.Scanner interface func (f *Foo) Scan(value interface{}) error { switch value := value.(type) { case int64: *f = Foo(value) default: return fmt.Errorf("Invalid database type: %T %v", value, value) } return nil }

Solution

1. fmt.Errorf(format, args)Returns the error value created usingerrors.New(str), wherestris the format String (your error message).

2. Line*f = Foo(value)Converts theint64value to theFootype and assigns it to the method receiver (notefis a pointer).

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