无法使用 double 类型的左值初始化“id _NonNull"类型的参数 [英] Cannot initialize a parameter of type 'id _NonNull' with an lvalue of type double

问题描述

目标 C:

我有多个 double、long long、NSString 和 int 类型的变量，我想将它们放入一个数组中，以便在 CSV 文件中作为单行打印

I have multiple variables of type double, long long, NSString and int which I want to put in an array to be printed as a single line in a CSV file

NSArray *ValArray = [NSArray arrayWithObjects: var1, var2, var3, var4, var5, nil];

NSArray *ValArray = [NSArray arrayWithObjects: var1, var2, var3 , var4, var5, nil];

这里 var1 是 double 类型，var2,var3 是 long long 类型.

Here var1 is of type double and var2,var3 are of the type long long.

这给了我一个语法错误，说无法在 var1 处用 double 类型的左值初始化类型为 'id _NonNull' 的参数"

This gives me a syntax error saying that "Cannot initialize a parameter of type 'id _NonNull' with an lvalue of type double" at var1

我是 Objective C 的新手，无法弄清楚我做错了什么.

I'm a newbie in Objective C and unable to figure out what I'm doing wrong.

推荐答案

Objective-C 中NSArray(和NSDictionary)的内容必须是对象.所有标量类型 int double 等都不是对象.

The contents of NSArray (and NSDictionary) in Objective-C must be objects. All scalar types int double etc. are not objects.

有一个简单的解决方案:

There is an easy solution:

将所有标量类型包装在快捷方式 NSNumber 初始值设定项 @()

Wrap all scalar types in the shortcut NSNumber initializer @()

 double var1 = 12.0;
 NSString *var2 = @"Foo";
 NSArray *valArray = [NSArray arrayWithObjects: @(var1), var2, nil];

或者更短

 NSArray *valArray = @[@(var1), var2];

要从数组中取回 double 类型，您必须编写

To get the double type back from the array you have to write

 double var3 = valArray[0].doubleValue;

附注:变量名应该以小写字母开头.

Side note: Variable names are supposed to start with a lowercase letter.

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