Go Enumerations: Difference between revisions
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=Overview= | =Overview= | ||
Go does not have formal enums, but the language allows for sets of related, yet distinct <code>int</code> constants. They represent a property that has several distinct possible <code>int</code> values, like the days of the weeks or the months of the year. | Go does not have formal enums, but the language allows for sets of related, yet distinct <code>int</code> constants. They represent a property that has several distinct possible <code>int</code> values, like the days of the weeks or the months of the year. | ||
These auto-incrementing <code>int</code> constants are declared using a special syntax involving the <code>const</code> keyword, parentheses and the [[Go_Language#Pre-Declared_Constants|pre-declared constant]] <code>[[Go_iota|iota]]</code>: | |||
<syntaxhighlight lang='go'> | <syntaxhighlight lang='go'> | ||
type DayOfTheWeek int | type DayOfTheWeek int | ||
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) | ) | ||
</syntaxhighlight> | </syntaxhighlight> | ||
Only the first constant in the series declares its type and an expression involving <code>iota</code>. The simplest is <code>iota</code> itself, but more complex expressions can be used. During the initialization, the compiler advances through the list of constants, and for each advancement, <code>iota</code> is incremented with 1. It starts with <code>0</code>. | |||
To make the enumeration constants visible outside the package, they need to start with a capital letter. | To make the enumeration constants visible outside the package, they need to start with a capital letter. | ||
Revision as of 23:03, 12 September 2024
External
Internal
Overview
Go does not have formal enums, but the language allows for sets of related, yet distinct int constants. They represent a property that has several distinct possible int values, like the days of the weeks or the months of the year.
These auto-incrementing int constants are declared using a special syntax involving the const keyword, parentheses and the pre-declared constant iota:
type DayOfTheWeek int
const (
MON DayOfTheWeek = iota
TUE
WED
THU
FRI
SAT
SUN
)
Only the first constant in the series declares its type and an expression involving iota. The simplest is iota itself, but more complex expressions can be used. During the initialization, the compiler advances through the list of constants, and for each advancement, iota is incremented with 1. It starts with 0.
To make the enumeration constants visible outside the package, they need to start with a capital letter.
Conversion to and from string representations:
type DayOfTheWeek int
const (
MON DayOfTheWeek = iota
TUE
WED
THU
FRI
SAT
SUN
)
var dayOfTheWeekToString = []string{
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
"Sunday",
}
func (s DayOfTheWeek) String() string {
return dayOfTheWeekToString[s]
}
func StringToDayOfTheWeek(s string) DayOfTheWeek {
for i, v := range dayOfTheWeekToString {
if s == v {
return DayOfTheWeek(i)
}
}
return DayOfTheWeek(-1)
}