I know I can iterate over a map m by,
for k, v := range m { ... }
and look for a key but is there a more efficient way of testing a key's existence in a map? Thanks. I couldn't find an answer in the language spec.
转载于:https://stackoverflow.com/questions/2050391/how-to-check-if-a-map-contains-a-key-in-go
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One line answer:
if val, ok := dict["foo"]; ok {
//do something here
}
if statements in Go can include both a condition and an initialization statement. The example above uses both:
initializes two variables - val will receive either the value of "foo" from the map or a "zero value" (in this case the empty string) and ok will receive a bool that will be set to true if "foo" was actually present in the map
evaluates ok, which will be true if "foo" was in the map
If "foo" is indeed present in the map, the body of the if statement will be executed and val will be local to that scope.
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