state

Does React keep the order for state updates?

由 血红的双手。 提交于 2019-11-26 03:01:57
问题 I know that React may perform state updates asynchronously and in batch for performance optimization. Therefore you can never trust the state to be updated after having called setState . But can you trust React to update the state in the same order as setState is called for the same component? different components? Consider clicking the button in the following examples: 1. Is there ever a possibility that a is false and b is true for: class Container extends React.Component { constructor

How to save RecyclerView's scroll position using RecyclerView.State?

由 倾然丶 夕夏残阳落幕 提交于 2019-11-26 02:49:51
I have a question about Android's RecyclerView.State . I am using a RecyclerView, how could I use and bind it with RecyclerView.State? My purpose is to save the RecyclerView's scroll position . Nikola Despotoski How do you plan to save last saved position with RecyclerView.State ? You can always rely on ol' good save state. Extend RecyclerView and override onSaveInstanceState() and onRestoreInstanceState() : @Override protected Parcelable onSaveInstanceState() { Parcelable superState = super.onSaveInstanceState(); LayoutManager layoutManager = getLayoutManager(); if(layoutManager != null &&

Updating an object with setState in React

由 筅森魡賤 提交于 2019-11-26 02:15:58
问题 Is it at all possible to update object\'s properties with setState? Something like: this.state = { jasper: { name: \'jasper\', age: 28 }, } I have tried: this.setState({jasper.name: \'someOtherName\'}); and this: this.setState({jasper: {name: \'someothername\'}}) The first results in a syntax error and the second just does nothing. Any ideas? 回答1: There are multiple ways of doing this, since state update is a async operation, so to update the state object, we need to use updater function with

Why does stringstream >> change value of target on failure?

由 萝らか妹 提交于 2019-11-26 02:10:31
问题 From Stroustrup\'s TC++PL, 3rd Edition, Section 21.3.3: If we try to read into a variable v and the operation fails, the value of v should be unchanged (it is unchanged if v is one of the types handled by istream or ostream member functions). The following example appears to contradict the above quote. Based on the above quote, I was expecting the value of v to remain unchanged -- but it gets zeroed. What\'s the explanation for this apparent contradictory behaviour? #include <iostream>

Does C++ support compile-time counters?

由 試著忘記壹切 提交于 2019-11-26 01:46:54
问题 For the purpose of introspection, sometimes I\'ve wanted to automatically assign serial numbers to types, or something similar. Unfortunately, template metaprogramming is essentially a functional language, and as such lacks global variables or modifiable state which would implement such a counter. Or is it? Example code by request: #include <iostream> int const a = counter_read; counter_inc; counter_inc; counter_inc; counter_inc; counter_inc; int const b = counter_read; int main() { std::cout

How to prevent custom views from losing state across screen orientation changes

由 我的梦境 提交于 2019-11-26 01:24:57
问题 I\'ve successfully implemented onRetainNonConfigurationInstance() for my main Activity to save and restore certain critical components across screen orientation changes. But it seems, my custom views are being re-created from scratch when the orientation changes. This makes sense, although in my case it\'s inconvenient because the custom view in question is an X/Y plot and the plotted points are stored in the custom view. Is there a crafty way to implement something similar to

Where to write to localStorage in a Redux app?

由 一曲冷凌霜 提交于 2019-11-26 01:06:03
问题 I want to persist some parts of my state tree to the localStorage. What is the appropriate place to do so? Reducer or action? 回答1: Reducer is never an appropriate place to do this because reducers should be pure and have no side effects. I would recommend just doing it in a subscriber: store.subscribe(() => { // persist your state }) Before creating the store, read those persisted parts: const persistedState = // ... const store = createStore(reducer, persistedState) If you use

How to save RecyclerView&#39;s scroll position using RecyclerView.State?

由 风格不统一 提交于 2019-11-26 01:04:55
问题 I have a question about Android\'s RecyclerView.State. I am using a RecyclerView, how could I use and bind it with RecyclerView.State? My purpose is to save the RecyclerView\'s scroll position . 回答1: How do you plan to save last saved position with RecyclerView.State ? You can always rely on ol' good save state. Extend RecyclerView and override onSaveInstanceState() and onRestoreInstanceState() : @Override protected Parcelable onSaveInstanceState() { Parcelable superState = super

AngularJS ui router passing data between states without URL

由 ⅰ亾dé卋堺 提交于 2019-11-25 23:30:08
问题 I am facing this problem of passing data between two states without exposing the data in the url, it\'s like user cannot really directly land on this state. For example. I have two states \"A\" and \"B\". I am doing some server call in state \"A\" and passing the response of the call to state \"B\". The response of the server call is a string message, which is quite long, so i cannot expose that in the url. So is there any way in angular ui router to pass data between states, without using

How to declare global variables in Android?

由 夙愿已清 提交于 2019-11-25 21:38:02
问题 I am creating an application which requires login. I created the main and the login activity. In the main activity onCreate method I added the following condition: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ... loadSettings(); if(strSessionString == null) { login(); } ... } The onActivityResult method which is executed when the login form terminates looks like this: @Override public void onActivityResult(int requestCode
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