Why Avoid Late Variables in Dart ??

𝗛𝗼𝘄 𝗟𝗮𝘁𝗲 𝗩𝗮𝗿𝗶𝗮𝗯𝗹𝗲𝘀 𝗰𝗮𝗻 𝗯𝗲 𝗩𝘂𝗹𝗻𝗲𝗿𝗮𝗯𝗹𝗲?

Instance fields can be initialized in 4 ways:

1. At the point of protestation
2. In a constructor argument using 'this'
3. In the constructor’s initializer list before the law in braces starts.
4. Anywhere Differently

4 is problematic since the preface of null safety. By the time the constructor body( the law in braces) starts, the object must be completely initialized so each of its fields are usable. So if it isn't initialized in 1, 2, or 3, it fails to collect.
𝐖𝐞 𝐜𝐚𝐧 𝐟𝐢𝐱 𝐭𝐡𝐢𝐬 𝐛𝐲' 𝐥𝐚𝐭𝐞' 𝐤𝐞𝐲𝐰𝐨𝐫𝐝.😃

It literally means “ I'll initialize it latterly ”. And you got no error.
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⚠️ 𝐁𝐮𝐭 𝐡𝐞𝐫𝐞 𝐚𝐫𝐞 𝐭𝐡𝐞 𝐫𝐞𝐚𝐬𝐨𝐧𝐬 𝐰𝐡𝐲 𝐬𝐡𝐨𝐮𝐥𝐝 𝐰𝐞 𝐬𝐡𝐨𝐮𝐥𝐝 𝐚𝐯𝐨𝐢𝐝 𝐥𝐚𝐭𝐞 𝐯𝐚𝐫𝐢𝐚𝐛𝐥𝐞𝐬:

𝟏- 𝐍𝐨 𝐜𝐨𝐦𝐩𝐢𝐥𝐞 - 𝐭𝐢𝐦𝐞 𝐜𝐡𝐞𝐜𝐤 𝐟𝐨𝐫 𝐢𝐧𝐢𝐭𝐢𝐚𝐥𝐢𝐳𝐚𝐭𝐢𝐨𝐧

Still, you only know this at runtime when the program fails, If you forget to initialize a late variable. Basically, you say “ Trust me to initialize d ever before it's read for the first time ”. So the compiler skips the initialization check and inserts a runtime check.

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𝟐- 𝐑𝐮𝐧𝐭𝐢𝐦𝐞 𝐜𝐡𝐞𝐜𝐤𝐬 𝐚𝐫𝐞 𝐬𝐤𝐢𝐩𝐩𝐞𝐝 𝐚𝐭 𝐡𝐢𝐠𝐡𝐞𝐫 𝐨𝐩𝐭𝐢𝐦𝐢𝐳𝐚𝐭𝐢𝐨𝐧 𝐥𝐞𝐯𝐞𝐥𝐬

There's a stir to allow skipping the initialization checks in some shapes. This may beget segfault which is harder to probe than an ordinary exception.

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𝟑- 𝐓𝐚𝐤𝐞𝐬 𝐦𝐨𝐫𝐞 𝐦𝐞𝐦𝐨𝐫𝐲

Your program needs to know if a late variable has been initialized or not. For this, the compiler frequently creates a retired internal variable that takes memory.

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𝟒- 𝐀𝐝𝐝𝐢𝐭𝐢𝐨𝐧𝐚𝐥 𝐫𝐞𝐚𝐝 𝐚𝐧𝐝 ‘ 𝐢𝐟 ’ 𝐛𝐞𝐟𝐨𝐫𝐞 𝐞𝐚𝐜𝐡 𝐫𝐞𝐚𝐝

Every time you read a late variable the program must insure it's initialized, so a redundant check is added.

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𝟓- 𝐀𝐝𝐝𝐢𝐭𝐢𝐨𝐧𝐚𝐥 𝐰𝐫𝐢𝐭𝐞 𝐛𝐞𝐟𝐨𝐫𝐞 𝐞𝐚𝐜𝐡 𝐰𝐫𝐢𝐭𝐞.

Every time you write to a late variable the program sets the internal flag to note that it's initialized.

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Hopefully, that helped. Did it? 😃

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Areeba Farooq