<p>Hey <a href="/r/golang" rel="nofollow">/r/golang</a> !</p>
<p>So I am trying/learning xorm ( <a href="http://xorm.io/" rel="nofollow">http://xorm.io/</a> )</p>
<p>In one of my tables I have a column which value is random, in the sense that the default value is the result of the sql function RANDOM() (I'm using PostgreSQL, but this should apply to other rdbmses too).</p>
<p>I have a struct modeled accordingly:</p>
<pre><code>type MyType struct {
...
random_value float64 `xorm:"DOUBLE NOT NULL DEFAULT random()"`
}
</code></pre>
<p>I realized that upon instantiating a struct of type MyStruct, since go defaults numeric types to zero (and other types to the relative null/zero/void value), the random_value field of every struct will get the value 0, which is a valid float64 value.</p>
<p>Thus, the rdbms is never going to execute the random() function in order to set the value of that column.</p>
<p><strong>First question</strong>: is there a way to instruct xorm to omit a field when constructing the INSERT sql query ?</p>
<p>I tried working around this behaviour: In the "Events" section of the documentation ( <a href="http://gobook.io/read/go-xorm/manual-en-us/chapter-12/" rel="nofollow">http://gobook.io/read/go-xorm/manual-en-us/chapter-12/</a> ) is explained how to intercept and handle events such as insertion, update, deletion and so on.</p>
<p>It is done by defining, for example, a BeforeInsert method on the struct, like this:</p>
<pre><code>func (self MyType) BeforeInsert() {
...
}
</code></pre>
<p>I tried using this technique to set the value of the random_value field.
The problem is that this way of defining the method is incapable of modifying the value of fields in the struct since the struct is passed by value.</p>
<p>I suspect the correct way to implement this would have been passing the struct by pointer (which is also more memory-efficient), like this:</p>
<pre><code>func (self *MyType) BeforeInsert() {
...
}
</code></pre>
<p>I tried implementing this, but such variation does not get called at all (I verified this by doing some Println, the old and dumb way).</p>
<p><strong>Second question</strong>: How do I customize a struct before insertion? Apparently you can have read access to all members of your struct but no write-access.</p>
<p>I have the feel that xorm is a very nice library which works very well until your use case falls in the ones envisioned by its creator, but fails very badly when you're trying to do something <em>particular</em>, outside the usual web-related CRUD. Also, the documentation is very basic and in some circumstances not so nice (the web pages at <a href="http://gobook.io/read/go-xorm/manual-en-us/" rel="nofollow">http://gobook.io/read/go-xorm/manual-en-us/</a> render a div incorrectly overlapping, and I had to supply my own css fix via stylish firefox extension to have something readable). Also, the source code lacks documentation, resulting in a godoc very little useful.</p>
<p>I would greatly appreciate hints and suggestions regarding my problem, as well as suggestions to other libraries that do not have such problems.</p>
<h2>Thanks in advance,</h2>
<p>znpy</p>
