92 lines
3.9 KiB
Markdown
92 lines
3.9 KiB
Markdown
## Common errors and how to solve them
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### SIGSEGV: Illegal storage access. (Attempt to read from nil?)
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This happens due to using a null pointer, it can be caused by several situations:
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**calling status-go with invalid parameters**
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Calling status-go with a json that is missing a field somewhere can cause status-go to crash somewhere or throw an exception that is not being caught
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**listening for non existing events**
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If an event in which a corresponding `emit` does not exist, it can cause this error
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```nimrod=
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events.on("event-does-not-exist") do(a: Args):
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appState.addChannel("test")
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appState.addChannel("test2")
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```
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**parsing json**
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when working with json, this error could be triggered for several reasons
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* accessing a property that doesn't exist
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* get the value type that doesn't match the value in the json
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* `if payload["contentType"].str == 2:` will crash because the value of contentType is `2` not `"2"`
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* something extracting a string with `value.str` instead of `$value` (sometimes `.getStr`)
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### Error: attempting to call undeclared routine
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this happens due something missing in the QTObject, it's caused for when a proc is not marked as a slot, not being public, not part of a variant, missing the self attribute or not mapped in a qproperty if it is an accesor
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*TODO: add practical examples*
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### Unsupported conversion of X to metatype
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this can happen due to a method being exposed to QT as a slot but using an object (like a model X) that is not a QtObject.
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possible solutions:
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- make the object a QtObject (usually only recommended if it's in the view only)
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- remove the {.slot.} pragma if it's not being called from QML anyway
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- change the method to receive params individually and then build the model inside the method
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### typeless parameters are obsolete
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typically means types are missing for a method parameters
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### attempting to call undeclared routine
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routine is likely not public or is being declared after the method calling it
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### QML Invalid component body specification
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This error happens when a `Component` has multiple children, it must only contain one child, to fix it, put the component children inside a `Item {}`
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### QML TypeError: Property 'setFunctionName' of object SomeView(0x7fa4bf55b240) is not a function
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Likely the function is missing a `{.slot.}` pragma
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### QML input text value not being updated
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If you are using an `Input` QML prop, to get the current value use `idName.TextField.text` instead of `idName.text`
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### QMutex: destroying locked mutex
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a common scenario this error can happen is when trying to immediatly access something in status-go when the app starts before the node is ready. it can also happen due to 2 threads attempting to call & change something from status-go at the same time
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## Warnings
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### QML anchor warnings
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Those look like
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```
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Cannot specify top, bottom, verticalCenter, fill or centerIn anchors for items inside Column. Column will not function.
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```
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or
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```
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Detected anchors on an item that is managed by a layout. This is undefined behavior; use Layout.alignment instead.
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```
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Those mean that you used anchors on an element that is manged by a Layout. Those are ColumnLayouts, StackLayouts, etc.
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The first child of anything in a "Something"Layout will not have access to anchors (they will throw warnings).
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First thing to ask yourself, do you really need a Layout? That's the easiest way to fix it. Unless you really need your block to be a row or a column that needs to go next/under another, use an Item or similar. Usually, you can still do the same effect anyway with anchors on the siblings
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If you really need the Layout, then one way to fix is to set the first child of the Layout an `Item` and then every other child inside the `Item`. That way, all the children can use anchors. You can set
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```
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Layout.fillHeight: true
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Layout.fillWidth: true
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```
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on the `Item` to make it fill the whole parent so that nothing else needs to be changed.
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