英文:
What does args := []interface{}{} mean in golang?
问题
这段代码看起来可以用作一个可以填充任意类型的列表，但我不理解语法。为什么有两组{}？
args := []interface{}{}
args = append(args, check.ID, checkNumber)
err := db.Exec(query, args...).Error
这段代码中的两组{}用于创建一个空的接口类型切片（slice），即args。接着，使用append函数将check.ID和checkNumber添加到args切片中。最后，args切片被传递给db.Exec函数的可变参数args...，以便作为参数传递给该函数。
英文:
It looks like it can be used as a list that can be filled with any types, but I don't understand the syntax. Why are there two set of {}?
args := []interface{}{}
args = append(args, check.ID, checkNumber)
err := db.Exec(query, args...).Error
答案1
得分: 5
让我们从内部语法到外部语法逐步构建起来。请按照我的描述中的链接，详细了解每个语法元素的解释。
interface{}是一个接口的类型规范，没有方法。通常称为空接口。所有类型都满足空接口。[]interface{}是空接口的slice。[]interface{}{}是一个包含空接口元素的slice的复合字面量表达式。
第一组 {} 是接口声明的一部分。接口中没有方法。
第二组 {} 是用于表示该切片的复合字面量表达式。切片中没有元素。
顺便提一下，问题中的代码可以简化为：
args := interface{}{check.ID, checkNumber}
err := db.Exec(query, args...).Error
进一步简化为：
err := db.Exec(query, check.ID, checkNumber).Error
编译器会自动从可变参数构建 []interface{}。
英文:
Let's build this up from the inner syntax to the outer syntax. Follow the links in my description for a detailed explanation of each syntax element.
interface{}is a type specification for an interface with no methods. This is commonly called the empty interface. All types satisfy the empty interface.[]interface{}is a slice of the empty interface.[]interface{}{}is a composite literal expression for a slice of empty interface containing no elements.
The first set of {} is part of the interface declaration. There are no methods in the interface.
The second set of {} is part of the composite literal expression for the slice. There are no elements in the slice.
As a side note, the code in the question can be reduced to:
args := interface{}{check.ID, checkNumber}
err := db.Exec(query, args...).Error
and further to:
err := db.Exec(query, check.ID, checkNumber).Error
The compiler automatically constructs the []interface{} from variadic arguments.
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