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Updated FAQ (markdown)

Benoît Blanchon
2016-09-29 11:39:44 +02:00
parent 1e0bfa97fe
commit 6e3168e7f2
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FAQ.md

@@ -13,6 +13,7 @@
- [How to write a function that works with both `JsonArray` and `JsonObject`?](#how-to-write-a-function-that-works-with-both-jsonarray-and-jsonobject)
- [How to assign a `JsonArray` or `JsonObject`?](#how-to-assign-a-jsonarray-or-jsonobject)
- [Part 2 - Serialization questions](#part-2---serialization-questions)
- [Why some parts are missing?](#why-some-parts-are-missing)
- [How to compute the JSON length?](#how-to-compute-the-json-length)
- [How to create complex nested objects?](#how-to-create-complex-nested-objects)
- [The first serialization succeeds, why do the next ones fail?](#the-first-serialization-succeeds-why-do-the-next-ones-fail)
@@ -182,7 +183,7 @@ See issues [#160](https://github.com/bblanchon/ArduinoJson/issues/160), [#203](h
### How to reuse a `JsonBuffer`?
`StaticJsonBuffer` and `DynamicJsonBuffer` are designed to be throwaway memory pools, they are not intended to be reused.
`StaticJsonBuffer` and `DynamicJsonBuffer` are designed to be throwaway memory pools, they are not intended to be reused.
As a consequence, using a global `JsonBuffer` is almost always a bad idea.
If you believe you need to reuse a `JsonBuffer`, it's because [you're not using the library correctly](https://github.com/bblanchon/ArduinoJson/wiki/FAQ#whats-the-best-way-to-use-the-library).
@@ -193,7 +194,7 @@ Imagine a `clear()` function is available, someone could write:
```c++
JsonObject& myObject = jsonBuffer.createObject();
jsonBuffer.clear();
jsonBuffer.clear();
JsonArray& myArray = jsonBuffer.createArray();
```
@@ -292,7 +293,7 @@ void myFunction(JsonVariant variant)
JsonArray& array = variant;
// ...
}
else if (variant.is<JsonObject&>())
else if (variant.is<JsonObject&>())
{
JsonObject& object = variant;
// ...
@@ -336,6 +337,21 @@ See issues [#341](https://github.com/bblanchon/ArduinoJson/issues/341) and [#343
## Part 2 - Serialization questions
### Why some parts are missing?
Example: you want to write `{"p1":[0, 1]}`, but instead you get `{"p1":[]}`.
This is because the `StaticJsonBuffer` too small.
Solution: Increase the size of the `StaticJsonBuffer` or switch to a `DynamicJsonBuffer`.
See also:
* [What are the differences between StaticJsonBuffer and DynamicJsonBuffer?](#what-are-the-differences-between-staticjsonbuffer-and-dynamicjsonbuffer)
* [How to determine the buffer size?](#how-to-determine-the-buffer-size)
* [JsonBuffer size calculator](https://rawgit.com/bblanchon/ArduinoJson/master/scripts/buffer-size-calculator.html)
* Issue [#360](https://github.com/bblanchon/ArduinoJson/issues/360)
### How to compute the JSON length?
@@ -731,11 +747,11 @@ But you can enumerate all the key-value pairs in the object, by using iterators:
char json[] = "{\"key\":\"value\"}";
JsonObject& object = jsonBuffer.parseObject(json);
for(JsonObject::iterator it=object.begin(); it!=object.end(); ++it)
for(JsonObject::iterator it=object.begin(); it!=object.end(); ++it)
{
const char* key = it->key;
if (it->value.is<char*>()) {
if (it->value.is<char*>()) {
const char* value = it->value;
// ...
}
@@ -776,4 +792,4 @@ ssid = network["ssid"].as<const char*>();
ssid = network["ssid"].as<String>();
```
See issue [#118](https://github.com/bblanchon/ArduinoJson/issues/118), [#146](https://github.com/bblanchon/ArduinoJson/issues/146) and [#197](https://github.com/bblanchon/ArduinoJson/issues/197).
See issue [#118](https://github.com/bblanchon/ArduinoJson/issues/118), [#146](https://github.com/bblanchon/ArduinoJson/issues/146) and [#197](https://github.com/bblanchon/ArduinoJson/issues/197).