Novice, ask some simple event handling mechanisms of the wepy Mini Program framework

question 1. Why can the event function outside the methods object be triggered when the element triggers the event ? The strange thing is that the button button cannot trigger the event function outside the methods object. Why is that?
question 2. Why the emit event function can only trigger functions in the methods object of the parent component? Cannot trigger the event function of outside the object?
[I have read the document; but there is no detailed description. I don"t know if I didn"t look carefully.
is very tangled. Are there any great gods you meet or can you talk about the principle?

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b34bb9-2bf66.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b34bb9-2bf66.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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