While trying to use couch-go and looking at the source, I’ve come across some things I don’t understand.
Is function wrapper needed?
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resp, err := client.Get(full_url)
log.Printf("resp: %v err: %v", resp, err)
if err == nil {
func() {
defer resp.Body.Close()
defer conn.Close()
tc := timeoutClient{resp.Body, conn, timeout}
largest = handler(&tc)
}()
} else {
log.Printf("Error in stream: %v", err)
time.Sleep(time.Second * 1)
}
Why the separate function wrapper here? Why not just call:
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defer resp.Body.Close()
defer conn.Close()
tc := timeoutClient{resp.Body, conn, timeout}
largest = handler(&tc)
directly?
How to elegantly dump a request body?
I was trying to debug something, and I wanted to print out the json string before it was being parsed, and here’s what I ended up doing:
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body, err0 := ioutil.ReadAll(r.Body)
bodyStr := string(body)
log.Printf("body: %v err: %v", bodyStr, err0)
newBody := bytes.NewBuffer(body)
d := json.NewDecoder(newBody)
// d := json.NewDecoder(r.Body) <-- orig code
if err := d.Decode(results); err != nil {
log.Printf("Decode err: %v", err)
return err
}
it seems like there should be a slicker way, like maybe rewinding the r.Body Reader?
Answer : yes, there is a much slicker way, io.TeeReader
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d := json.NewDecoder(io.TeeReader(r.Body, os.Stdout))
Using new() with a map — does this look right?
According to “The Way To Go” (book), you are not supposed to be using new() with maps. However I did this in one case:
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type Document map[string]interface{}
func (game Game) fetchLatestGameDoc() (doc Document, err error) {
fetchedDoc := new(Document)
err = game.db.Retrieve(GAME_DOC_ID, fetchedDoc)
if err == nil {
doc = *fetchedDoc
}
return
}
is there a better way? When I tried using make(), I got the error err: json: Unmarshal(non-pointer checkerlution.Document). Using make() followed by & didn’t work either.
Type Assertion hell
I’m trying to get some data that’s fairly deep in some json, and ended up doing a lot of awkward feeling type assertions:
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func (game Game) checkGameDocInChanges(changes Changes) bool {
foundGameDoc := false
changeResultsRaw := changes["results"]
changeResults := changeResultsRaw.([]interface{})
for _, changeResultRaw := range changeResults {
changeResult := changeResultRaw.(map[string]interface{})
docIdRaw := changeResult["id"]
docId := docIdRaw.(string)
if strings.Contains(docId, GAME_DOC_ID) {
foundGameDoc = true
}
}
return foundGameDoc
}
there must be a better way?
Also I didn’t get why this didn’t work:
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type ChangeItem map[string]interface{}
...
changeResult := changeResultRaw.(ChangeItem)
to make it work I had to change it to:
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changeResult := changeResultRaw.(map[string]interface{})
Getting unexpected float64 back from JSON, had to do awkward type conversions
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func (game Game) isOurTurn(gameDoc Document) bool {
activeTeamRaw := gameDoc["activeTeam"]
activeTeam := int(activeTeamRaw.(float64))
return activeTeam == game.ourTeamId
}
Json snippet:
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{"_id":"game:checkers","activeTeam":0}
Can’t check for nil
I have these structs:
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type Game struct {
gameState GameState
}
type GameState struct {
...
}
and in a loop, I set the gameState field of the Game object to value. I’m trying to detect if it’s the first pass through the loop with this:
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isFirstGame := (game.gameState == nil)
but I get the error cannot convert nil to type GameState
