UnicodeString :: Delete方法 [英] UnicodeString::Delete Method

问题描述

我有一个Unicode字符串，我希望限制为30个字符.我从查询中填充字符串，所以我不知道开头的长度.我只想剪掉30岁以后的所有字符.我找到了 UnicodeString::Delete() 方法，但是我不知道如何使用它.

I have a Unicode string that I want to limit to 30 characters. I populate the string from a query, so I don't know the length to begin with. I want to simply snip off all of the characters past 30. I found the UnicodeString::Delete() method, but I don't know how to use it.

我尝试这样做无济于事

mystring = <code here to populate the unicode string mystring>
Delete(mystring, 30, 100);

推荐答案

您实际上是在尝试致电 System::Delete() ，仅对Delphi不可用，对C ++不可用.在内部，UnicodeString::Delete()使用this作为要操作的字符串来调用System::Delete().

You are actually trying to call System::Delete(), which is not available to C++, only to Delphi. Internally, UnicodeString::Delete() calls System::Delete() using this as the string to manipulate.

UnicodeString::Delete()是非静态类方法.您需要在字符串对象本身上调用它，而不是作为单独的函数调用它.另外，Delete()是1索引而不是0索引:

UnicodeString::Delete() is a non-static class method. You need to call it on the string object itself, not as a separate function. Also, Delete() is 1-indexed, not 0-indexed:

mystring.Delete(31, MaxInt);

如果要使用0索引，请使用 UnicodeString::Delete0() 代替:

If you want to use 0-indexing, use UnicodeString::Delete0() instead:

mystring.Delete0(30, MaxInt);

但是， UnicodeString::SetLength() 方法将是在这种情况下更合适:

However, the UnicodeString::SetLength() method would be more appropriate in this situation:

if (mystring.Length() > 30)
    mystring.SetLength(30);

或者，您可以使用 UnicodeString::SubString() / UnicodeString::SubString0() :

Alternatively, you can use UnicodeString::SubString()/UnicodeString::SubString0():

mystring = mystring.SubString(1, 30);

mystring = mystring.SubString0(0, 30);

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