How is the WeChat cash withdrawal message realized?

A promise is a promise. There is an ancient saying: "If you keep your word, you will get what you want." In a word, even if four good horses pull it, it's hard to chase it. It can be seen that everyone attaches great importance to what they say.

However, people always say the wrong things, such as:

In order to solve the troubles of the disabled, WeChat launched the "WeChat Withdraw" function in version 5.3. 1. 16, which provides the withdrawal option for messages sent within 2 minutes:

The user presses and holds the sent message (including the picture) and chooses to withdraw from multiple choices.

Then the question is coming,

Why can a sent message be easily recalled?

In the Korean drama "You from the Stars", Professor Li Wu did not hesitate to use two "killer weapons": time travel and space stillness, in order to prevent Qian Songyi from seeing the subconscious confession message.

In fact, you don't have to envy Professor Du. Since we have the WeChat recall function, every WeChat user can compete with the superpower and easily withdraw messages.

So, how can WeChat extract information from two mobile phones at the same time without the help of super powers?

Take MobleA sending messages and withdrawing messages to MobileB as an example:

A. When A.MobileA sends a message, it will generate a unique UniqueMsgID in the world on its own WeChat client and attach the UniqueMsgID to the message body to be sent.

B. When B.MobileB receives the message, it stores the message body and displays the message.

C. when C.MoblieA withdraws the message, MobleA knows the UniqueMsgID of each message body she sent and the message that needs to be withdrawn, and attaches the UniqueMsgID of the message to the withdrawal command.

When D.Moblieb receives the recall command, it will look up the corresponding message body in its own database according to the UniqueMsgID in the recall command, and then display the recall effect.

Why can WeChat only withdraw messages for 2 minutes?

The era of mobile Internet urges everyone to be in an era of asynchronous information processing. Most people need some time to process information. In contrast, two minutes seems a little too short. They often find that they have expired when they want to quit.

So, do we need to set a withdrawal period?

The answer is undoubtedly yes. In the dialogue between the two sides, if the withdrawal time is not set, there will be two kinds of harm:

A. If the withdrawal time is not set after the information is sent, it is likely that the receiver has seen some information that has been sent for a long time, and the further withdrawal of the sender will make the relationship between the two parties more embarrassing and even cause unnecessary misunderstanding.

B. After the information is sent, if there is no limit on the withdrawal time, the sender can withdraw any historical message, which will lead to incomplete conversation context and affect the user experience.

Then why is the withdrawal time 2 minutes? Can't it be a little more or less?

In this regard, after analyzing big data, the WeChat product team believes that from the perspective of information recipients, 2 minutes is the average time from receiving to reading a message. The withdrawal time is less than 2 minutes, which will maintain the integrity of the context to the greatest extent and give people a stable user experience.

If it is less than 2 minutes, the publisher may not have time to realize the information error and have missed the opportunity to withdraw it;

If it is longer than 2 minutes, the probability that the message will be read by the receiver will be greatly improved, and the sender does not need to withdraw the message. In addition, withdrawing information sent a long time ago will also destroy the coherence of the context and seriously affect the dialogue experience and effect.

Instead of setting a time limit, why not prompt the other party to read in the recall function?

Although 2 minutes is the average time from receiving to reading the information, we can't know when the receiver will read the sent information, which will lead to the recall function sometimes not being so timely, thus falling into the famous "Schrodinger's cat" problem.