When Should You Use Parentheses to Initialize Go Structs?

Parenthesis Initialization in Go Structs

In Go, initializing a struct typically involves assigning values directly to its fields using curly braces, as seen in the example item1 := Item{1, "Foo"}. However, another method involves initializing a struct within parentheses, as in item2 := (Item{2, "Bar"}).

At first glance, these two initialization methods may appear identical. However, using parentheses holds a specific significance when employed within certain contexts.

For instance, when initializing a struct within an if statement, parentheses become essential. Without them, Go's parser faces an ambiguity between the struct's opening brace being part of the composite literal or the if statement's body.

To eliminate this ambiguity, parentheses must be used around the struct initialization, as in if i := (Item{3, "a"}); i.Id == 3 {}. This explicitly clarifies that the opening brace belongs to the struct initialization, making the code valid.

Furthermore, parentheses can offer a stylistic preference for readability in some scenarios. While the method of initialization with curly braces is more prevalent, using parentheses may provide a clearer visual representation when multiple initialization statements are chained together.

Ultimately, both initialization methods yield the same outcome for stand-alone struct creation. However, using parentheses becomes mandatory within if statements and may offer visual advantages in certain situations.

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