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explain Exists() function

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Josh Baker 2016-08-12 16:26:06 -07:00 committed by GitHub
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README.md
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@ -52,7 +52,7 @@ A path is a series of keys separated by a dot.
A key may contain special wildcard characters '\*' and '?'. A key may contain special wildcard characters '\*' and '?'.
To access an array value use the index as the key. To access an array value use the index as the key.
To get the number of elements in an array use the '#' character. To get the number of elements in an array use the '#' character.
The dot and wildcard character can be escaped with '\'. The dot and wildcard characters can be escaped with '\'.
``` ```
{ {
"name": {"first": "Tom", "last": "Anderson"}, "name": {"first": "Tom", "last": "Anderson"},
@ -69,13 +69,12 @@ The dot and wildcard character can be escaped with '\'.
"fav\.movie" >> "Deer Hunter" "fav\.movie" >> "Deer Hunter"
``` ```
## Result Type ## Result Type
GJSON supports the json types `string`, `number`, `bool`, and `null`. GJSON supports the json types `string`, `number`, `bool`, and `null`.
Arrays and Objects are returned as their raw json types. Arrays and Objects are returned as their raw json types.
The `Result` type holds one of these types: The `Result` type holds one of these:
``` ```
bool, for JSON booleans bool, for JSON booleans
@ -84,7 +83,7 @@ string, for JSON string literals
nil, for JSON null nil, for JSON null
``` ```
To get the value call the `Value()` method: To get the Go value call the `Value()` method:
```go ```go
@ -92,15 +91,9 @@ result.Value() // interface{} which may be nil, string, float64, or bool
// Or just get the value in one step. // Or just get the value in one step.
gjson.Get(json, "name.last").Value() gjson.Get(json, "name.last").Value()
// Check for the existence of a value.
if gjson.Get(json, "name.last").Exists(){
println("value exists")
}
``` ```
To directly access the value from its original type: To directly access the value:
```go ```go
result.Type // can be String, Number, True, False, Null, or JSON result.Type // can be String, Number, True, False, Null, or JSON
@ -109,6 +102,25 @@ result.Num // holds the float64 number
result.Raw // holds the raw json result.Raw // holds the raw json
``` ```
## Check for the existence of a value
Sometimes you may want to see if the value actually existed in the json document.
```
value := gjson.Get(json, "name.last")
if !value.Exists() {
println("no last name")
} else {
println(value.String())
}
// Or as one step
if gjson.Get(json, "name.last").Exists(){
println("has a last name")
}
```
## Performance ## Performance
Benchmarks of GJSON alongside [encoding/json](https://golang.org/pkg/encoding/json/), Benchmarks of GJSON alongside [encoding/json](https://golang.org/pkg/encoding/json/),