javascript Knockout：写入和读取计算属性
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Knockout: writing and reading a computed property
提问by Matteo Pagliazzi
I have a model with two property: title and content and what I want to do is:
我有一个具有两个属性的模型：标题和内容，我想做的是：
If title has a value, use it but in case it's blank use the first 20 chars + "..." from content.
如果 title 有值，请使用它，但如果它是空白的，请使用内容中的前 20 个字符 + "..."。
This is the model:
这是模型：
function Note(title, content) {
var self = this;
self.content = ko.observable(content);
self.title = ko.computed({
read: function(){
if(!title){
var content = self.content();
if(content) return content.substring(0,19) + "...";
}
},
write: function(title){
return title;
}
});
}
Title value gets correctly updated from content but it's impossible (for me) to get writing directly on title working..
标题值从内容中正确更新，但（对我而言）不可能直接在标题上书写工作..
The only problem in RP Niemeyer answer is that i must have only on property for reading/writing, is that possible?
RP Niemeyer 回答中的唯一问题是我必须只拥有用于读/写的财产，这可能吗？
回答by RP Niemeyer
When creating your writeable computed observable, you will want to have a separate observable to contain the actual title.
在创建可写的计算 observable 时，您将需要一个单独的 observable 来包含实际标题。
More like:
更像：
function Note(title, content) {
var self = this;
self.content = ko.observable(content);
self.title = ko.observable(title);
self.displayTitle = ko.computed({
read: function() {
var title = self.title();
if (!title) {
var content = self.content();
if (content) return content.substring(0, 19) + "...";
}
return title;
},
write: self.title
});
}?
