Clarification about modifying properties in handle class

1 次查看（过去 30 天）
Bandar
Bandar 2021-7-20
回答： Steven Lord 2021-7-21
Take a look at the following class
classdef Counter < handle
properties
count
end
methods
function this = Counter(x)
if nargin == 1
this.count = x;
end
end
function increment(this)
this.count = this.count + 1;
end
end
end
In the constructor, if the argument is zero, count is initliazed according to its value in properties block. In the preceding code, count is empty. It is interesting to notice that in this particular case, calling increment() has no effect on incrementing count. I have to explicitly initializing it with any value in order to make `increment()` works. Any suggestions why I need to explicitly initialize properties?

请先登录，再回答此问题。

采纳的回答

Steven Lord
Steven Lord 2021-7-21
Ran in:
In the preceding code, count is empty.
That is correct, the default value for that propery is the 0-by-0 empty double array [] as stated in the "Property Default Values" section of this documentation page.
calling increment() has no effect on incrementing count
That is also correct.
x = []
x = []
y = x + 1
y = []
The 1 is scalar "expanded" to be a 0-by-0 and a 0-by-0 plus a 0-by-0 results in a 0-by-0.
Any suggestions why I need to explicitly initialize properties?
Because you don't want the default value for that property to be empty in this case.
By the way, despite you mentioning "handle class" in the subject of this post, this behavior holds for value classes as well.

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Construct and Work with Object Arrays 的更多信息

标签

产品


版本

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by